1. Minisatellites, originally developed for forensic DNA fingerprinting and profiling, have also provided extremely informative systems for analysing processes of tandem repeat DNA turnover in the human genome. 2. Minisatellite instability involves distinct mutation processes in somatic and germline cells. In sperm, tandem repeat instability most likely arises at meiosis as a by-product of high-frequency meiotic recombination events occurring in and near minisatellites. Instability is not an intrinsic property of minisatellite repeat DNA, but instead appears to be controlled by flanking recombination initiation elements. 3. Minisatellites not only show high-frequency spontaneous mutation in the germline, but also appear to be very sensitive to mutation induction by ionizing radiation, both in experimentally irradiated mice and in human populations exposed following the Chernobyl disaster; the mechanisms of mutation induction by radiation remain enigmatic.