diff --git a/mercurial/hook.py b/mercurial/hook.py
--- a/mercurial/hook.py
+++ b/mercurial/hook.py
@@ -37,10 +37,18 @@ def _pythonhook(ui, repo, name, hname, f
         try:
             obj = __import__(modname)
         except ImportError:
+            e1 = sys.exc_type, sys.exc_value, sys.exc_traceback
             try:
                 # extensions are loaded with hgext_ prefix
                 obj = __import__("hgext_%s" % modname)
             except ImportError:
+                e2 = sys.exc_type, sys.exc_value, sys.exc_traceback
+                if ui.tracebackflag:
+                    ui.warn(_('exception from first failed import attempt:\n'))
+                ui.traceback(e1)
+                if ui.tracebackflag:
+                    ui.warn(_('exception from second failed import attempt:\n'))
+                ui.traceback(e2)
                 raise util.Abort(_('%s hook is invalid '
                                    '(import of "%s" failed)') %
                                  (hname, modname))
diff --git a/mercurial/ui.py b/mercurial/ui.py
--- a/mercurial/ui.py
+++ b/mercurial/ui.py
@@ -15,7 +15,7 @@ import config, util, error
 class ui(object):
     def __init__(self, src=None):
         self._buffers = []
-        self.quiet = self.verbose = self.debugflag = self._traceback = False
+        self.quiet = self.verbose = self.debugflag = self.tracebackflag = False
         self._reportuntrusted = True
         self._ocfg = config.config() # overlay
         self._tcfg = config.config() # trusted
@@ -101,7 +101,7 @@ class ui(object):
         if self.verbose and self.quiet:
             self.quiet = self.verbose = False
         self._reportuntrusted = self.configbool("ui", "report_untrusted", True)
-        self._traceback = self.configbool('ui', 'traceback', False)
+        self.tracebackflag = self.configbool('ui', 'traceback', False)
 
         # update trust information
         self._trustusers.update(self.configlist('trusted', 'users'))
@@ -337,13 +337,16 @@ class ui(object):
 
         return t
 
-    def traceback(self):
+    def traceback(self, exc=None):
         '''print exception traceback if traceback printing enabled.
         only to call in exception handler. returns true if traceback
         printed.'''
-        if self._traceback:
-            traceback.print_exc()
-        return self._traceback
+        if self.tracebackflag:
+            if exc:
+                traceback.print_exception(exc[0], exc[1], exc[2])
+            else:
+                traceback.print_exc()
+        return self.tracebackflag
 
     def geteditor(self):
         '''return editor to use'''
diff --git a/tests/test-hook b/tests/test-hook
--- a/tests/test-hook
+++ b/tests/test-hook
@@ -248,4 +248,18 @@ echo "pre-commit.test = python:`pwd`/tes
 cd ../repo
 hg commit
 
+cd ../../b
+echo '# make sure --traceback works on hook import failure'
+cat > importfail.py <<EOF
+import somebogusmodule
+# dereference something in the module to force demandimport to load it
+somebogusmodule.whatever
+EOF
+
+echo '[hooks]' > .hg/hgrc
+echo 'precommit.importfail = python:importfail.whatever' >> .hg/hgrc
+
+echo a >> a
+hg --traceback commit -Ama 2>&1 | grep '^\(exception\|Traceback\|ImportError\)'
+
 exit 0
diff --git a/tests/test-hook.out b/tests/test-hook.out
--- a/tests/test-hook.out
+++ b/tests/test-hook.out
@@ -163,3 +163,11 @@ hooks.commit.auto=<function autohook>
 # test python hook configured with python:[file]:[hook] syntax
 hook works
 nothing changed
+# make sure --traceback works on hook import failure
+exception from first failed import attempt:
+Traceback (most recent call last):
+ImportError: No module named somebogusmodule
+exception from second failed import attempt:
+Traceback (most recent call last):
+ImportError: No module named hgext_importfail
+Traceback (most recent call last):