TitraSim is a Win32 program for simulating acid-base titration experiments where an arbitrary number of acids and/or bases may be involved in both sample and titrator. The program comes with archives containing the most common standard acids/bases and their pK-values. The archive can be extended by adding new species or data referring to other solvent systems or to non-standard temperatures. Simulating the theoretical titration curves for a mixture of such species is therefore a matter of a few mouse clicks. Real experimental titration curves (stored as volume/pH-value couples in ASCII-files) can be imported into TitraSim and compared with simulated ones. The determination of analytical species concentrations and/or pK-values can be accomplished in this way either by "trial and error" (TitraSim-Standard) or by making use of the non-linear fitting procedure implemented into TitraSim-Professional.