Using a modified method for the determination of the genotype of the neurotrophin 3 Gly/Glu polymorphism by PCR, we investigated allele frequencies in patients suffering from different psychiatric diseases as well as in healthy controls. There was a much lower frequency of the allele Glu among Caucasians (0.006) than previously reported for a Japanese population (0.203). No homozygotes and only three heterozygotes for the rare allele could be detected: the latter belonged to the patient group and suffered from endogenous depression (two patients) and hebephrenia (one patient). Due to its very low frequency it seems unlikely that the allele Glu plays a decisive role in the aetiopathogenesis of schizophrenic psychoses or other psychiatric diseases. However, it cannot be excluded that it represents a risk or vulnerability factor.