Typing of polymorphisms on the human chromosome X (ChrX) has become a standard technique in forensic genetics, and a growing number of short tandem repeats (STRs) has been established. Knowledge of marker recombination is of great significance especially when ChrX typing is used in forensic kinship testing. It is known that meiotic recombination is not a simple function of physical distance but crossing over events tend to be clustered. Information on genetic distances between markers can be gathered by family studies and by interpolation of gene bank data such as the Rutgers map. We typed DNA samples of pedigrees consisting of mothers with several sons and grandfather-mother-son constellations and report here the recombination characteristics of 39 ChrX STRs in up to 135 meioses.