diff --git a/doc/OpenSTA.odt b/doc/OpenSTA.odt
index f62a343c..20a0359f 100644
Binary files a/doc/OpenSTA.odt and b/doc/OpenSTA.odt differ
diff --git a/doc/OpenSTA.pdf b/doc/OpenSTA.pdf
index a35bbbfa..a99d3a7f 100644
Binary files a/doc/OpenSTA.pdf and b/doc/OpenSTA.pdf differ
diff --git a/include/sta/Search.hh b/include/sta/Search.hh
index a5d0a521..85a59916 100644
--- a/include/sta/Search.hh
+++ b/include/sta/Search.hh
@@ -176,9 +176,12 @@ public:
   bool isClock(const Vertex *vertex) const;
   // Vertices on propagated generated clock source paths.
   bool isGenClkSrc(const Vertex *vertex) const;
-  // The set of clocks that arrive at vertex.
+  // The set of clocks that arrive at vertex in the clock network.
   ClockSet clocks(const Vertex *vertex) const;
   ClockSet clocks(const Pin *pin) const;
+  // Clock domains for a vertex.
+  ClockSet clockDomains(const Vertex *vertex) const;
+  ClockSet clockDomains(const Pin *pin) const;
   void visitStartpoints(VertexVisitor *visitor);
   void visitEndpoints(VertexVisitor *visitor);
   bool havePathGroups() const;
@@ -526,6 +529,9 @@ protected:
   void clocks(const Vertex *vertex,
               // Return value.
               ClockSet &clks) const;
+  void clockDomains(const Vertex *vertex,
+                    // Return value.
+                    ClockSet &clks) const;
 
   ////////////////////////////////////////////////////////////////
 
diff --git a/include/sta/Sta.hh b/include/sta/Sta.hh
index cbb91c82..0fdccfb9 100644
--- a/include/sta/Sta.hh
+++ b/include/sta/Sta.hh
@@ -595,8 +595,10 @@ public:
 		      bool thru_disabled,
 		      bool thru_constants);
 
-  // The set of clocks that reach pin.
+  // The set of clocks that arrive at vertex in the clock network.
   ClockSet clocks(const Pin *pin);
+  // Clock domains for a pin.
+  ClockSet clockDomains(const Pin *pin);
 
   void checkSlewLimitPreamble();
   // Return pins with the min/max slew limit slack.
diff --git a/search/Property.cc b/search/Property.cc
index 459ca7a0..f67764a8 100644
--- a/search/Property.cc
+++ b/search/Property.cc
@@ -882,6 +882,10 @@ getProperty(const Pin *pin,
     ClockSet clks = sta->clocks(pin);
     return PropertyValue(&clks);
   }
+  else if (stringEqual(property, "clock_domains")) {
+    ClockSet clks = sta->clockDomains(pin);
+    return PropertyValue(&clks);
+  }
   else if (stringEqual(property, "activity")) {
     PwrActivity activity = sta->findClkedActivity(pin);
     return PropertyValue(&activity);
diff --git a/search/Search.cc b/search/Search.cc
index bdaa9e0a..d1e25b1a 100644
--- a/search/Search.cc
+++ b/search/Search.cc
@@ -3018,6 +3018,42 @@ Search::timingDerate(Vertex *from_vertex,
   }
 }
 
+ClockSet
+Search::clockDomains(const Vertex *vertex) const
+{
+  ClockSet clks;
+  clockDomains(vertex, clks);
+  return clks;
+}
+
+void
+Search::clockDomains(const Vertex *vertex,
+                     // Return value.
+                     ClockSet &clks) const
+{
+  VertexPathIterator path_iter(const_cast<Vertex*>(vertex), this);
+  while (path_iter.hasNext()) {
+    Path *path = path_iter.next();
+    const Clock *clk = path->clock(this);
+    if (clk)
+      clks.insert(const_cast<Clock *>(clk));
+  }
+}
+
+ClockSet
+Search::clockDomains(const Pin *pin) const
+{
+  ClockSet clks;
+  Vertex *vertex;
+  Vertex *bidirect_drvr_vertex;
+  graph_->pinVertices(pin, vertex, bidirect_drvr_vertex);
+  if (vertex)
+    clockDomains(vertex, clks);
+  if (bidirect_drvr_vertex)
+    clockDomains(bidirect_drvr_vertex, clks);
+  return clks;
+}
+
 ClockSet
 Search::clocks(const Vertex *vertex) const
 {
diff --git a/search/Sta.cc b/search/Sta.cc
index ad3f42be..29c1319d 100644
--- a/search/Sta.cc
+++ b/search/Sta.cc
@@ -4681,6 +4681,14 @@ Sta::clocks(const Pin *pin)
   return search_->clocks(pin);
 }
 
+ClockSet
+Sta::clockDomains(const Pin *pin)
+{
+  searchPreamble();
+  search_->findAllArrivals();
+  return search_->clockDomains(pin);
+}
+
 ////////////////////////////////////////////////////////////////
 
 InstanceSet