Variation in the number of tandem repeats of a 48 base pair (bp) unit was found in the gene of the dopamine D4 receptor (DRD4). The number of repetitions of the 48bp unit was shown to influence the binding of clozapine, which suggests that different alleles may function differently in vivo and affect the pathogenesis of schizophrenia. Genotypes of DRD4 polymorphism were analyzed for 47 schizophrenic probands who had at least one living sibling with a diagnosis of schizophrenia, 35 unaffected siblings of the schizophrenic proband, 42 sporadic schizophrenic patients, and 43 healthy controls without a family history of psychosis. There was no significant difference in genotypic or allelic distributions among the four groups. Significant differences in the frequencies of two- and seven-repeats alleles between the Chinese and Caucasians controls were noted. The present study did not support that a particular allele or genotype of the 48bp-repeat of DRD4 was associated with schizophrenia.