DNA was isolated from the peripheral blood samples of 27 patients with schizophrenia receiving clozapine maintenance treatment, and the pharmacokinetics‐related genes (CYP1A2, CYP2B6, CYP2C19, CYP2D6, CYP3A5, ABCG2, and SLCO1B1) were genotyped. The gene discussed is CYP2D6; the disease is schizophrenia.