Cannabis can induce schizophrenic-like symptoms in healthy individuals. A principal active ingredient of cannabis, delta-9-tetrahydrocannabinol, acts in the brain on a specific receptor, termed the cannabinoid receptor 1 (CNR1). The human gene for CNR1 is mapped to chromosome 6q14-15, and linkage studies have produced evidence for a schizophrenia-susceptibility locus in this region. To explore a possible role for CNR1 in the pathogenesis of schizophrenic disorders, we used an association study to genotype the CNR1 polymorphism for 127 schizophrenic patients and 146 control subjects. The results demonstrate no association between CNR1 genotypes and schizophrenic disorders (P = 0.409), with these negative findings suggesting that, for Chinese populations, the (AAT)n triplet repeat in the promoter region of the CNR1 gene is not directly involved in the pathogenesis of schizophrenic disorders.