diff --git a/README b/README
index d3d0fb0cc3181842295b194aaca823a6be9cf92d..569e6c9450c0fd6fd4e91b9f5f17916e8156f1c9 100644
--- a/README
+++ b/README
@@ -12,11 +12,12 @@ This requires GSL 1.2 or higher (freely available from
 http://sources.redhat.com/gsl/) and FLTK 1.1.x (configured with OpenGL
 support; freely available from http://www.fltk.org). You can use the
 --with-fltk-prefix and --with-gsl-prefix configure options (or define
-the FLTK_DIR and GSL_DIR environment variables) if the libraries are
-not installed in their default locations. Please note that compiling
-the Windows version requires the Cygwin tools (freely available from
-http://www.cygwin.com) and a "cygwin-enabled" version of FLTK (i.e.,
-you have to configure FLTK with "./configure --enable-cygwin").
+the FLTK_PREFIX and GSL_PREFIX environment variables) if the libraries
+are not installed in their default locations. Please note that
+compiling the Windows version requires the Cygwin tools (freely
+available from http://www.cygwin.com) and a "cygwin-enabled" version
+of FLTK (i.e., you have to configure FLTK with "./configure
+--enable-cygwin").
 
 To install a non-graphical version of Gmsh (that does not require FLTK
 nor OpenGL), type
diff --git a/configure b/configure
index dc3c087c5bf3d86c45526980ef3b3a4f5a7ccd1a..8da4454d18febf7e45939266c3b1e53d666b0a48 100755
--- a/configure
+++ b/configure
@@ -1325,40 +1325,30 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 if test "${with_fltk_prefix+set}" = set; then
   withval="$with_fltk_prefix"
   FLTK_PREFIX=$withval
-else
-  FLTK_PREFIX="$FLTK_DIR"
 fi;
 
 # Check whether --with-gsl-prefix or --without-gsl-prefix was given.
 if test "${with_gsl_prefix+set}" = set; then
   withval="$with_gsl_prefix"
   GSL_PREFIX=$withval
-else
-  GSL_PREFIX="$GSL_DIR"
 fi;
 
 # Check whether --with-jpeg-prefix or --without-jpeg-prefix was given.
 if test "${with_jpeg_prefix+set}" = set; then
   withval="$with_jpeg_prefix"
   JPEG_PREFIX=$withval
-else
-  JPEG_PREFIX="$JPEG_DIR"
 fi;
 
 # Check whether --with-png-prefix or --without-png-prefix was given.
 if test "${with_png_prefix+set}" = set; then
   withval="$with_png_prefix"
   PNG_PREFIX=$withval
-else
-  PNG_PREFIX="$PNG_DIR"
 fi;
 
 # Check whether --with-z-prefix or --without-z-prefix was given.
 if test "${with_z_prefix+set}" = set; then
   withval="$with_z_prefix"
   Z_PREFIX=$withval
-else
-  Z_PREFIX="$Z_DIR"
 fi;
 
 # Check whether --enable-gsl or --disable-gsl was given.
diff --git a/configure.in b/configure.in
index 980c0aa72c49cc2e1664242b9428fa1d5566ad14..56936e6107fa617eddc496eb0d56104cd4fe82d3 100644
--- a/configure.in
+++ b/configure.in
@@ -1,4 +1,4 @@
-dnl $Id: configure.in,v 1.70 2005-06-20 20:28:54 geuzaine Exp $
+dnl $Id: configure.in,v 1.71 2005-06-24 18:14:15 geuzaine Exp $
 dnl
 dnl Copyright (C) 1997-2005 C. Geuzaine, J.-F. Remacle
 dnl
@@ -32,23 +32,23 @@ dnl Parse '--with' command-line options
 AC_ARG_WITH(fltk-prefix,
             AC_HELP_STRING([--with-fltk-prefix=PFX],
                            [prefix where FLTK is installed]),
-            [FLTK_PREFIX=$withval],[FLTK_PREFIX="$FLTK_DIR"])
+            [FLTK_PREFIX=$withval])
 AC_ARG_WITH(gsl-prefix,
             AC_HELP_STRING([--with-gsl-prefix=PFX],
                            [prefix where GSL is installed]),
-            [GSL_PREFIX=$withval],[GSL_PREFIX="$GSL_DIR"])
+            [GSL_PREFIX=$withval])
 AC_ARG_WITH(jpeg-prefix,
             AC_HELP_STRING([--with-jpeg-prefix=PFX],
                            [prefix where the JPEG library and includes are installed]),
-            [JPEG_PREFIX=$withval],[JPEG_PREFIX="$JPEG_DIR"])
+            [JPEG_PREFIX=$withval])
 AC_ARG_WITH(png-prefix,
             AC_HELP_STRING([--with-png-prefix=PFX],
                            [prefix where the PNG library and includes are installed]),
-            [PNG_PREFIX=$withval],[PNG_PREFIX="$PNG_DIR"])
+            [PNG_PREFIX=$withval])
 AC_ARG_WITH(z-prefix,
             AC_HELP_STRING([--with-z-prefix=PFX],
                            [prefix where the ZLIB library and includes are installed]),
-            [Z_PREFIX=$withval],[Z_PREFIX="$Z_DIR"])
+            [Z_PREFIX=$withval])
 
 dnl Parse '--enable' command line options
 AC_ARG_ENABLE(gsl,