diff --git a/networks.rkt b/networks.rkt
index 817b851..b7a8b91 100644
--- a/networks.rkt
+++ b/networks.rkt
@@ -33,6 +33,7 @@
                [build-syntactic-interaction-graph (-> network-form? graph?)]
                [interaction? (-> network? domain-mapping/c variable? variable? boolean?)]
                [get-interaction-sign (-> network? domain-mapping/c variable? variable? (or/c #f -1 0 1))]
+               [build-interaction-graph (-> network? domain-mapping/c graph?)]
                [build-all-states (-> domain-mapping/c (listof state?))]
                [make-same-domains (-> (listof variable?) generic-set? domain-mapping/c)]
                [make-boolean-domains (-> (listof variable?) (hash/c variable? (list/c #f #t)))]
@@ -504,6 +505,37 @@
     (check-equal? (get-interaction-sign n-multi 123-doms 'y 'z) -1)
     (check-equal? (get-interaction-sign n-multi 123-doms 'y 't) 0)))
 
+;;; Given a network, builds its interaction graph.  The graph has
+;;; variables as nodes and has a directed edge from x to y if
+;;; interaction? returns #t for these variables, in this order.
+(define (build-interaction-graph network doms)
+  (define vars (hash-keys network))
+  (unweighted-graph/directed
+   (for*/list ([x vars]
+               [y vars]
+               #:when (interaction? network doms x y))
+     (list x y))))
+
+(module+ test
+  (test-case "build-interaction-graph"
+    (define n-bool (network-form->network
+                    (hash 'x '(not y)
+                          'y 'x
+                          'z '(and y z)
+                          't '(or (and (not x) y)
+                                  (and x (not y))))))
+    (define bool-doms (make-boolean-domains '(x y z t)))
+    (check-equal? (graphviz (build-interaction-graph n-bool bool-doms))
+                  "digraph G {\n\tnode0 [label=\"y\"];\n\tnode1 [label=\"z\"];\n\tnode2 [label=\"x\"];\n\tnode3 [label=\"t\"];\n\tsubgraph U {\n\t\tedge [dir=none];\n\t\tnode0 -> node2;\n\t\tnode1 -> node1;\n\t}\n\tsubgraph D {\n\t\tnode0 -> node3;\n\t\tnode0 -> node1;\n\t\tnode2 -> node3;\n\t}\n}\n")
+    (define n-multi (network-form->network
+                     (hash 'x '(min (+ y 1) 2)
+                           'y '(max (- y 1) 0)
+                           'z '(- 2 y)
+                           't '(abs (- y 1)))))
+    (define 123-doms (make-same-domains '(x y z t) '(0 1 2)))
+    (check-equal? (graphviz (build-interaction-graph n-multi 123-doms))
+                  "digraph G {\n\tnode0 [label=\"y\"];\n\tnode1 [label=\"z\"];\n\tnode2 [label=\"x\"];\n\tnode3 [label=\"t\"];\n\tsubgraph U {\n\t\tedge [dir=none];\n\t\tnode0 -> node0;\n\t}\n\tsubgraph D {\n\t\tnode0 -> node2;\n\t\tnode0 -> node3;\n\t\tnode0 -> node1;\n\t}\n}\n")))
+
 ;;; ====================
 ;;; Dynamics of networks
 ;;; ====================