Tscope is a C/C+ + programming library designed for programming experiments that run on Windows 2000/XP. It is intended for a public of experimental psychologists with moderate programming skills, who are accustomed to writing their own experimental programs for DOS but have not made the step to Windows-based programming yet. It provides molecular functions for graphics, sound, timing, randomization, and response registration. Together with ANSI-C standard library functions and the powerful C syntax, this set of functions gives the experimenter the opportunity to program virtually any experiment one can come up with. Tscope is completely based on free software, is distributed under the GNU General Public License, and is available at expsy.ugent.be/tscope. An integrated development environment for compiling and running Tscope programs is also freely available.