The aim of the present study was to develop a Swedish self-rating instrument for clinical aggression research based on the American Aggression Questionnaire (AQ), which measures physical aggression, verbal aggression, anger, and hostility. To test this adapted Aggression Questionnaire--revised Swedish version (AQ-RSV), it was mailed to 781 randomly selected individuals, aged 20-40 year. A total of 497 (64%) evaluable AQ-RSV inventories were obtained and analyzed statistically. Drop-out analysis showed that non-responders were most often male and significantly older than responders. Among the responders, AQ-RSV showed significant sex differences in all aggression subscales except Hostility. Aggression was found to vary with age, geographical region, and size of home community. The AQ and the AQ-RSV were comparable in correlations between the four aggression subscales and in alpha coefficients, which indicated considerable internal consistency. Development of the aggression-measuring instrument for Swedish conditions is important not only to study subtraits of aggression but to enable analyses of their relationships to neurobiological and psychiatric variables.