For setting up xschem with ngspice on Mac OS, I found I needed to add some arguments to the configure command for ngspice. They were: CFLAGS="-O2 -I/opt/X11/include/freetype2 -Wno-error=implicit-function-declaration" --x-includes=/opt/X11/include --x-libraries=/opt/X11/lib The entire string was: ./configure --enable-cider --enable-xspice --enable-openmp --enable-pss --enable-debug=no --prefix=/<path to>/ngspice-macos --enable-openmp CFLAGS="-O2 -I/opt/X11/include/freetype2 -Wno-error=implicit-function-declaration" LDFLAGS="-lomp" --x-includes=/opt/X11/include --x-libraries=/opt/X11/lib