diff --git a/README.md b/README.md
index 303cfbba..c92f26af 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 ## TODO
 
-* [ ] predicates
+* [x] predicates
 * [ ] negation
 * [ ] aggregation
 * [ ] stratum
diff --git a/src/data/expr.rs b/src/data/expr.rs
index 98a82225..85d2daba 100644
--- a/src/data/expr.rs
+++ b/src/data/expr.rs
@@ -1,4 +1,4 @@
-use std::collections::BTreeSet;
+use std::collections::{BTreeMap, BTreeSet};
 use std::fmt::{Debug, Formatter};
 
 use anyhow::Result;
@@ -19,13 +19,26 @@ pub enum ExprError {
 
 #[derive(Debug, Clone)]
 pub enum Expr {
-    Binding(Keyword),
-    BoundIdx(usize),
+    Binding(Keyword, Option<usize>),
     Const(DataValue),
     Apply(&'static Op, Box<[Expr]>),
 }
 
 impl Expr {
+    pub(crate) fn fill_binding_indices(&mut self, binding_map: &BTreeMap<Keyword, usize>) {
+        match self {
+            Expr::Binding(k, idx) => {
+                let found_idx = *binding_map.get(k).unwrap();
+                *idx = Some(found_idx)
+            }
+            Expr::Const(_) => {}
+            Expr::Apply(_, args) => {
+                for arg in args.iter_mut() {
+                    arg.fill_binding_indices(binding_map);
+                }
+            }
+        }
+    }
     pub(crate) fn bindings(&self) -> BTreeSet<Keyword> {
         let mut ret = BTreeSet::new();
         self.collect_bindings(&mut ret);
@@ -33,10 +46,9 @@ impl Expr {
     }
     pub(crate) fn collect_bindings(&self, coll: &mut BTreeSet<Keyword>) {
         match self {
-            Expr::Binding(b) => {
+            Expr::Binding(b, _) => {
                 coll.insert(b.clone());
             }
-            Expr::BoundIdx(_) => {}
             Expr::Const(_) => {}
             Expr::Apply(_, args) => {
                 for arg in args.iter() {
@@ -47,10 +59,7 @@ impl Expr {
     }
     pub(crate) fn eval(&self, bindings: &Tuple) -> Result<DataValue> {
         match self {
-            Expr::Binding(_) => {
-                unreachable!()
-            }
-            Expr::BoundIdx(i) => Ok(bindings.0[*i].clone()),
+            Expr::Binding(_, i) => Ok(bindings.0[i.unwrap()].clone()),
             Expr::Const(d) => Ok(d.clone()),
             Expr::Apply(op, args) => {
                 let args: Box<[DataValue]> = args.iter().map(|v| v.eval(bindings)).try_collect()?;
@@ -77,7 +86,7 @@ pub struct Op {
 
 impl Debug for Op {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
-        f.debug_tuple(self.name).field(&self.min_arity).finish()
+        write!(f, "{}", self.name)
     }
 }
 
diff --git a/src/parse/query.rs b/src/parse/query.rs
index ee8dba7a..1102a822 100644
--- a/src/parse/query.rs
+++ b/src/parse/query.rs
@@ -163,7 +163,7 @@ impl SessionTx {
             JsonValue::String(s) => {
                 let kw = Keyword::from(s as &str);
                 if kw.is_reserved() {
-                    Ok(Expr::Binding(kw))
+                    Ok(Expr::Binding(kw, None))
                 } else {
                     Ok(Expr::Const(DataValue::String(s.into())))
                 }
diff --git a/src/query/compile.rs b/src/query/compile.rs
index 992ca900..b48fff54 100644
--- a/src/query/compile.rs
+++ b/src/query/compile.rs
@@ -64,7 +64,7 @@ pub enum QueryCompilationError {
     #[error("op {0} is not a predicate")]
     NotAPredicate(&'static str),
     #[error("unsafe bindings in expression {0:?}: {1:?}")]
-    UnsafeBindingInPredicate(Expr, BTreeSet<Keyword>)
+    UnsafeBindingInPredicate(Expr, BTreeSet<Keyword>),
 }
 
 #[derive(Clone, Debug)]
@@ -140,7 +140,7 @@ impl Atom {
     pub(crate) fn into_predicate(self) -> Option<Expr> {
         match self {
             Atom::Predicate(e) => Some(e),
-            _ => None
+            _ => None,
         }
     }
     pub(crate) fn collect_bindings(&self, coll: &mut BTreeSet<Keyword>) {
@@ -417,9 +417,7 @@ impl SessionTx {
                     debug_assert_eq!(prev_joiner_vars.len(), right_joiner_vars.len());
                     ret = ret.join(right, prev_joiner_vars, right_joiner_vars);
                 }
-                Atom::Predicate(_) => {
-                    todo!()
-                }
+                Atom::Predicate(p) => ret = ret.filter(p.clone()),
                 Atom::Logical(_) => {
                     todo!()
                 }
diff --git a/src/query/eval.rs b/src/query/eval.rs
index a376f2bf..9acd07f8 100644
--- a/src/query/eval.rs
+++ b/src/query/eval.rs
@@ -34,8 +34,9 @@ impl SessionTx {
                     let mut collected = Vec::with_capacity(body.rules.len());
                     for rule in &body.rules {
                         let header = rule.head.iter().map(|t| &t.name).cloned().collect_vec();
-                        let relation =
+                        let mut relation =
                             self.compile_rule_body(&rule.body, rule.vld, &stores, &header)?;
+                        relation.fill_predicate_binding_indices();
                         collected.push((rule.head.clone(), rule.contained_rules(), relation));
                     }
                     Ok((k.clone(), collected))
diff --git a/src/query/relation.rs b/src/query/relation.rs
index 8c8902c0..27f273a1 100644
--- a/src/query/relation.rs
+++ b/src/query/relation.rs
@@ -6,6 +6,7 @@ use anyhow::Result;
 use itertools::Itertools;
 
 use crate::data::attr::Attribute;
+use crate::data::expr::Expr;
 use crate::data::keyword::Keyword;
 use crate::data::tuple::{Tuple, TupleIter};
 use crate::data::value::DataValue;
@@ -20,6 +21,44 @@ pub enum Relation {
     Derived(StoredDerivedRelation),
     Join(Box<InnerJoin>),
     Reorder(ReorderRelation),
+    Filter(FilteredRelation),
+}
+
+pub struct FilteredRelation {
+    parent: Box<Relation>,
+    pred: Expr,
+}
+
+impl FilteredRelation {
+    fn fill_binding_indices(&mut self) {
+        let parent_bindings: BTreeMap<_, _> = self
+            .parent
+            .bindings()
+            .into_iter()
+            .enumerate()
+            .map(|(a, b)| (b, a))
+            .collect();
+        self.pred.fill_binding_indices(&parent_bindings);
+    }
+    fn iter<'a>(
+        &'a self,
+        tx: &'a SessionTx,
+        epoch: Option<u32>,
+        use_delta: &BTreeSet<TempStoreId>,
+    ) -> TupleIter {
+        Box::new(
+            self.parent
+                .iter(tx, epoch, use_delta)
+                .filter_map(|tuple| match tuple {
+                    Ok(t) => match self.pred.eval_pred(&t) {
+                        Ok(true) => Some(Ok(t)),
+                        Ok(false) => None,
+                        Err(e) => Some(Err(e)),
+                    },
+                    Err(e) => Some(Err(e)),
+                }),
+        )
+    }
 }
 
 struct BindingFormatter<'a>(&'a [Keyword]);
@@ -63,8 +102,7 @@ impl Debug for Relation {
                 if r.left.is_unit() {
                     r.right.fmt(f)
                 } else {
-                    f
-                        .debug_tuple("Join")
+                    f.debug_tuple("Join")
                         .field(&BindingFormatter(&r.bindings()))
                         .field(&r.joiner)
                         .field(&r.left)
@@ -77,11 +115,34 @@ impl Debug for Relation {
                 .field(&r.new_order)
                 .field(&r.relation)
                 .finish(),
+            Relation::Filter(r) => f
+                .debug_tuple("Filter")
+                .field(&r.pred)
+                .field(&r.parent)
+                .finish(),
         }
     }
 }
 
 impl Relation {
+    pub(crate) fn fill_predicate_binding_indices(&mut self) {
+        match self {
+            Relation::Fixed(_) => {}
+            Relation::Triple(_) => {}
+            Relation::Derived(_) => {}
+            Relation::Join(r) => {
+                r.left.fill_predicate_binding_indices();
+                r.right.fill_predicate_binding_indices();
+            }
+            Relation::Reorder(r) => {
+                r.relation.fill_predicate_binding_indices();
+            }
+            Relation::Filter(f) => {
+                f.parent.fill_predicate_binding_indices();
+                f.fill_binding_indices()
+            }
+        }
+    }
     pub(crate) fn unit() -> Self {
         Self::Fixed(InlineFixedRelation::unit())
     }
@@ -126,6 +187,12 @@ impl Relation {
             new_order,
         })
     }
+    pub(crate) fn filter(self, filter: Expr) -> Self {
+        Relation::Filter(FilteredRelation {
+            parent: Box::new(self),
+            pred: filter,
+        })
+    }
     pub(crate) fn join(
         self,
         right: Relation,
@@ -786,6 +853,7 @@ impl Relation {
             Relation::Derived(_r) => Ok(()),
             Relation::Join(r) => r.do_eliminate_temp_vars(used),
             Relation::Reorder(r) => r.relation.eliminate_temp_vars(used),
+            Relation::Filter(_) => Ok(()),
         }
     }
 
@@ -796,6 +864,7 @@ impl Relation {
             Relation::Derived(_) => None,
             Relation::Join(r) => Some(&r.to_eliminate),
             Relation::Reorder(_) => None,
+            Relation::Filter(_) => None,
         }
     }
 
@@ -817,6 +886,7 @@ impl Relation {
             Relation::Derived(d) => d.bindings.clone(),
             Relation::Join(j) => j.bindings(),
             Relation::Reorder(r) => r.bindings(),
+            Relation::Filter(r) => r.parent.bindings(),
         }
     }
     pub fn iter<'a>(
@@ -834,6 +904,7 @@ impl Relation {
             Relation::Derived(r) => r.iter(epoch, use_delta),
             Relation::Join(j) => j.iter(tx, epoch, use_delta),
             Relation::Reorder(r) => r.iter(tx, epoch, use_delta),
+            Relation::Filter(r) => r.iter(tx, epoch, use_delta),
         }
     }
 }
@@ -909,7 +980,9 @@ impl InnerJoin {
                     self.materialized_join(tx, eliminate_indices, epoch, use_delta)
                 }
             }
-            Relation::Join(_) => self.materialized_join(tx, eliminate_indices, epoch, use_delta),
+            Relation::Join(_) | Relation::Filter(_) => {
+                self.materialized_join(tx, eliminate_indices, epoch, use_delta)
+            }
             Relation::Reorder(_) => {
                 panic!("joining on reordered")
             }
diff --git a/tests/creation.rs b/tests/creation.rs
index 28dbd49c..f3faa614 100644
--- a/tests/creation.rs
+++ b/tests/creation.rs
@@ -141,10 +141,10 @@ fn creation() {
             },
             {
                 "rule": "?",
-                "args": [["?n", "?a"], {"rule": "ff", "args": [{"person/id": "alice_amorist"}, "?a"]}, ["?a", "person/first_name", "?n"]]
+                "args": [["?n", "?a"], {"pred": "Neq", "args": ["?n", "Alice"]}, {"rule": "ff", "args": [{"person/id": "alice_amorist"}, "?a"]}, ["?a", "person/first_name", "?n"]]
             }
         ],
-        "out": {"friend": {"pull": "?a", "spec": ["*"]}}
+        // "out": {"friend": {"pull": "?a", "spec": ["*"]}}
     });
     let mut tx = db.transact().unwrap();
     let ret = tx.run_query(&query).unwrap();