Testosterone has been attributed importance for various aspects of behaviour. The aim of our study was to investigate the potential influence of 2 functional polymorphisms in the amino terminal of the androgen receptor on personality traits in men.We assessed and genotyped 141 men born in 1944 recruited from the general population. We used 2 different instruments: the Karolinska Scales of Personality and the Temperament and Character Inventory. For replication, we similarly assessed 63 men recruited from a forensic psychiatry study group.In the population-recruited sample, the lengths of the androgen receptor repeats were associated with neuroticism, extraversion and self-transcendence. The association with extraversion was replicated in the independent sample.Our 2 samples differed in size; sample 1 was of moderate size and sample 2 was small. In addition, the homogeneity of sample 1 probably enhanced our ability to detect significant associations between genotype and phenotype.Our results suggest that the repeat polymorphisms in the androgen receptor gene may influence personality traits in men.