To investigate the possible role of the dopamine transporter (DAT) gene in determining the phenotype in human subjects, allele frequencies for the 40-bp variable number of tandem repeats (VNTR) polymorphism at this site were compared between 117 Japanese normal controls and 118 schizophrenic patients, including six subgroups: early-onset, those with a family history, and those suffering from one of the following psychiatric symptoms at their first episode: delusion and hallucination; disorganization; bizarre behavior; and negative symptoms. No significant differences were observed between the group as a whole or any subgroup of schizophrenic patients and controls. The results indicate that VNTR polymorphism in the DAT gene is unlikely to be a major contributor to any of the psychiatric parameters examined in the present population of schizophrenic subjects.