diff --git a/simgear/Makefile.am b/simgear/Makefile.am
index b0581e42..b8c05870 100644
--- a/simgear/Makefile.am
+++ b/simgear/Makefile.am
@@ -4,18 +4,6 @@ else
 SERIAL_DIRS =
 endif
 
-# if HAVE_GDBM
-# GDBM_DIRS =
-# else
-# GDBM_DIRS = gdbm
-# endif
-
-if HAVE_ZLIB
-ZLIB_DIRS =
-else
-ZLIB_DIRS = zlib
-endif
-
 if HAVE_THREADS
 SGTHREAD_DIR = threads
 else
@@ -31,7 +19,6 @@ include_HEADERS = \
 	compiler.h constants.h sg_inlines.h sg_traits.hxx sg_zlib.h version.h
 
 SUBDIRS = \
-	$(ZLIB_DIRS) \
 	xml \
 	debug \
 	misc \
diff --git a/simgear/io/lowlevel.hxx b/simgear/io/lowlevel.hxx
index b866df2e..3595991d 100644
--- a/simgear/io/lowlevel.hxx
+++ b/simgear/io/lowlevel.hxx
@@ -29,12 +29,7 @@
 
 
 #include <stdio.h>
-
-#ifdef HAVE_ZLIB
-#  include <zlib.h>
-#else
-#  include <simgear/zlib/zlib.h>
-#endif
+#include <zlib.h>
 
 #include <plib/sg.h>
 
diff --git a/simgear/math/Makefile.am b/simgear/math/Makefile.am
index 794664d8..cb939c9f 100644
--- a/simgear/math/Makefile.am
+++ b/simgear/math/Makefile.am
@@ -1,11 +1,5 @@
 includedir = @includedir@/math
 
-if HAVE_ZLIB
-ZLIB_INCL =
-else
-ZLIB_INCL = -I$(top_srcdir)/src/zlib
-endif
-
 lib_LIBRARIES = libsgmath.a
 
 include_HEADERS = \
@@ -31,7 +25,7 @@ libsgmath_a_SOURCES = \
 	vector.cxx
 
 if OLD_AUTOMAKE
-INCLUDES += -I$(top_srcdir) $(ZLIB_INCL)
+INCLUDES += -I$(top_srcdir)
 else
-INCLUDES = -I$(top_srcdir) $(ZLIB_INCL)
+INCLUDES = -I$(top_srcdir)
 endif
diff --git a/simgear/misc/Makefile.am b/simgear/misc/Makefile.am
index 1be88870..3c846bf9 100644
--- a/simgear/misc/Makefile.am
+++ b/simgear/misc/Makefile.am
@@ -1,11 +1,5 @@
 includedir = @includedir@/misc
 
-if HAVE_ZLIB
-ZLIB_INCL =
-else
-ZLIB_INCL = -I$(top_srcdir)/src/zlib
-endif
-
 lib_LIBRARIES = libsgmisc.a
 
 include_HEADERS = \
@@ -36,7 +30,7 @@ props_test_SOURCES = props_test.cxx
 props_test_LDADD = libsgmisc.a ../xml/libsgxml.a ../debug/libsgdebug.a
 
 if OLD_AUTOMAKE
-INCLUDES += -I$(top_srcdir) $(ZLIB_INCL)
+INCLUDES += -I$(top_srcdir)
 else
-INCLUDES = -I$(top_srcdir) $(ZLIB_INCL)
+INCLUDES = -I$(top_srcdir)
 endif
diff --git a/simgear/misc/zfstream.hxx b/simgear/misc/zfstream.hxx
index 1dd3669e..bf9f1733 100644
--- a/simgear/misc/zfstream.hxx
+++ b/simgear/misc/zfstream.hxx
@@ -30,11 +30,7 @@
 
 #include <simgear/compiler.h>
 
-#ifdef HAVE_ZLIB
-#  include <zlib.h>
-#else
-#  include <simgear/zlib/zlib.h>
-#endif
+#include <zlib.h>
 
 // At least Irix needs this
 #ifdef SG_HAVE_NATIVE_SGI_COMPILERS
diff --git a/simgear/sg_zlib.h b/simgear/sg_zlib.h
index c8b41e06..3119167b 100644
--- a/simgear/sg_zlib.h
+++ b/simgear/sg_zlib.h
@@ -61,11 +61,7 @@
   #define sgclose(F)  (fclose((F)))
 #else
 
-#ifdef HAVE_ZLIB
   #include <zlib.h>
-#else
-  #include <simgear/zlib/zlib.h>
-#endif
 
   #define sgFile gzFile
 
diff --git a/simgear/simgear_config.h.in b/simgear/simgear_config.h.in
index 61b86781..f63fe4b2 100644
--- a/simgear/simgear_config.h.in
+++ b/simgear/simgear_config.h.in
@@ -50,9 +50,6 @@
 /* Define if you have the vprintf function.  */
 #undef HAVE_VPRINTF
 
-/* Define if you have zlib installed system wide.  */
-#undef HAVE_ZLIB
-
 /* Define as the return type of signal handlers (int or void).  */
 #undef RETSIGTYPE
 
diff --git a/simgear/xml/Makefile.am b/simgear/xml/Makefile.am
index bc01b91b..33c96bc2 100644
--- a/simgear/xml/Makefile.am
+++ b/simgear/xml/Makefile.am
@@ -1,11 +1,5 @@
 includedir = @includedir@/xml
 
-if HAVE_ZLIB
-ZLIB_INCL =
-else
-ZLIB_INCL = -I$(top_srcdir)/src/zlib
-endif
-
 lib_LIBRARIES = libsgxml.a
 
 include_HEADERS = \
@@ -25,7 +19,7 @@ libsgxml_a_SOURCES = \
 	xmltok_impl.h
 
 if OLD_AUTOMAKE
-INCLUDES += -I$(top_srcdir) $(ZLIB_INCL)
+INCLUDES += -I$(top_srcdir)
 else
-INCLUDES = -I$(top_srcdir) $(ZLIB_INCL)
+INCLUDES = -I$(top_srcdir)
 endif