On windows under current R-devel (r57066), R CMD INSTALL, for instance, invokes gcc with -I"$(R_HOME)/include" prior to any user-defined include paths. This means that a package cannot specify an alternative zlib.h, as a (reduced) version of this is in $(R_HOME)/include. One way around this is to redefine .o rules %.o: %.c $(CC) $(MY_ZFLAGS) $(ALL_CPPFLAGS) $(ALL_CFLAGS) -c $< -o $@ Is there a better way? Can the ordering of the include search path be altered in src/gnuwin32/fixed/etc/Makeconf:160-161? Martin -- Computational Biology Fred Hutchinson Cancer Research Center 1100 Fairview Ave. N. PO Box 19024 Seattle, WA 98109 Location: M1-B861 Telephone: 206 667-2793