Hi, It's been about 5 years since I faced this situation. I'm trying to link my program against the Thread module. Things go well until I do the ocamlopt compilation, then it aborts the make with the message: ocamlfind ocamlopt -thread -o sdsp.opt -package camlp4 -package threads -package unix -I ../src -I /usr/local/lib/ocaml/threads \ -thread -cclib threads.a nums.cmxa sdsp.cmxa threads/threads.cmxa \ readline.cmx scmMain.cmx File "_none_", line 1, characters 0-1: Error: No implementations provided for the following modules: Thread referenced from ../src/sdsp.cmxa(SdlPrims) make[1]: *** [sdsp.opt] Error 2 make: *** [subdirs] Error 2 Forgive the excessive number of -thread flags in there... this has been trial and error. I understand that it can't seem to find a .ml file to go along with the thread.mli, because there isn't one provided by the distribution. I also understand that the functionality of the thread module is made up largely of the posix threads C-code in the otherlibs directory. Somehow the system needs to be coaxed to look into the threads subdirectory in the lib/ocaml folder, but I am at wits end at this point.... This make is proceeding on Mac OS X 10.4 I'm sure it is possible to do this, because I have an ancient (unreadable) make script that does so for another system. Surely there is a very simple solution here, short of my inventing an entire Makefile script for this project. Eh? Thanks in advance... Dr. David McClain Chief Technical Officer Refined Audiometrics Laboratory 4391 N. Camino Ferreo Tucson, AZ 85750 email: dbm@refined-audiometrics.com phone: 1.520.390.3995 web: http://www.refined-audiometrics.com