Androgens exert their effects primarily by stimulating androgen receptors (ARs) and androgen activity has been implicated in antisocial or violent criminal behaviour. Exon 1 of the AR gene contains a highly polymorphic glutamine (CAG) repeat sequence. We tested the hypothesis that shorter AR CAG repeat polymorphisms, which have a greater AR gene expression, are related to violent criminal activity in Chinese males using a sample of 146 extremely violent criminals and 108 normal controls. The results show no association between the AR repeat length and violent convicts, although we found that there are more violent-criminal cases than control cases with the shorter (<17) AR gene trinucleotide repeat polymorphisms (7.5% vs. 1.9%; P=0.047). No correlation was found between the AR CAG repeat length and the first criminal record age in the violent-criminal group. The mean AR repeat length is not significantly different between substance dependence cases and antisocial personality disorder diagnosis in the violent criminals and normal controls. Our findings suggest that the AR CAG repeat polymorphism does not play a major role in the susceptibility of male violent criminal activity.