diff --git a/Makefile.am b/Makefile.am
index 8d8666f9..e24c89ad 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -94,8 +94,19 @@ endif
 lint:
 	for dir in lcr lib exec services tools test; do make -C $$dir lint; done
 
+.PHONY: doxygen
 doxygen:
-	mkdir -p doc/api && doxygen
+	@if [ "$(DOXYGEN)" = "" ] || [ "$(DOT)" = "" ] ; then \
+		echo "*********************************************" ; \
+		echo "***                                       ***" ; \
+		echo "*** You must install doxygen and graphviz ***" ; \
+		echo "*** to generate the API documentation.    ***" ; \
+		echo "***                                       ***" ; \
+		echo "*********************************************" ; \
+		exit 1 ; \
+	else \
+		mkdir -p doc/api && $(DOXYGEN) ; \
+	fi
 
 dist-clean-local:
 	rm -f autoconf automake autoheader test_lense.sh
diff --git a/configure.ac b/configure.ac
index 9beb38d7..4d304ff5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -63,6 +63,8 @@ AC_PROG_RANLIB
 AC_CHECK_PROGS([GROFF], [groff])
 AC_CHECK_PROGS([PKGCONFIG], [pkg-config])
 AC_CHECK_PROGS([AUGTOOL], [augtool])
+AC_CHECK_PROGS([DOT], [dot])
+AC_CHECK_PROGS([DOXYGEN], [doxygen])
 
 # Checks for libraries.
 AC_CHECK_LIB([dl], [dlopen])