Studies have shown that genetic components to some extent underlie behavioral disorders such as impulsive aggression and violence, and that central serotonergic mechanisms are involved in the development of such behavior. In the present study, we analyzed a polymorphism in the gene encoding the serotonin 2A receptor (5-HT2A -1438 G/A) in a group of Swedish criminals (n=97) and in a group of healthy Swedish blood donors (n=202). The 5-HT2A -1438 GG genotype was lower in the criminal group than in the control group (P=0.034). In accordance with previous results, no associations were found between the 5-HT2A -1438 G/A polymorphism and personality as measured by Karolinska Scales of Personality. Neither were there any associations between the studied polymorphism and the type of crime committed.