Human family and twin studies have established considerable heritable components influencing individual differences in personality traits as assessed by self-report questionnaires. We have investigated a trinucleotide repeat polymorphism in the androgen receptor gene and personality traits. Healthy Swedish subjects (n = 335) were assessed with the Karolinska Scales of Personality inventory. There were tendencies (P > or = 0.006) in some scales indicating possible relationships between the androgen receptor allele length and personality traits related to dominance and aggression. However, after correction for multiple testing, no significant differences were found. We conclude that no significant association could be found between the androgen receptor polymorphism investigated and any personality trait, although the tendencies found are worthwhile subjects for replication attempts.