Eleven drug-naive male schizophrenic patients with a mean ± SD age of 28.1 ± 7.9 years who met the DSM-IV criteria for schizophrenia or schizophreniform disorder were studied. Those with schizophreniform disorder at study entry met the criteria for schizophrenia at the 6-month follow-up. Exclusion criteria were current or past substance abuse and a history of alcohol-related problems, mood disorders, organic brain disease, and antipsychotic or antidepressant medication use. Initial diagnoses were made by the physicians in charge (Y.O., Y.N., K.N., or others), second diagnoses were made by secondary physicians (T.S. and F.Y. or M.I. and another physician) on the day of the PET scan with reference to the written history of the present illness by the physician in charge, and final diagnoses were made by 2 of the secondary physicians (T.S. and F.Y.) several months after the PET scan with reference to the follow-up information from the physicians in charge. All the physicians involved in these steps and procedures were psychiatrists. The patients were recruited from the outpatient units of 5 university-affiliated psychiatric hospitals and the psychiatric divisions of general hospitals in Tokyo and Chiba prefecture in Japan. The average ± SD onset age was 25.8 ± 8.4 years (range, 14.0-38.0 years), and the duration of illness ranged from 1 month to 8 years (average, 2.1 years). Psychopathology was assessed by the 18-item Oxford version of the Brief Psychiatric Rating Scale (BPRS) translated into Japanese (item score range, 0-6 points).16 The BPRS scores were completed by 2 of the authors(T.S. and F.Y.) and 1 other psychiatrist. The ratings were reviewed by these2 authors (T.S. and F.Y.) and 1 other psychiatrist after the patient interview, and disagreements were resolved by consensus; the consensus ratings were then used in this study. Positive and negative symptom scores were calculated as the sum of the following items.17 Positive symptom subscales were conceptual disorganization, mannerisms and posturing, hostility, grandiosity, suspiciousness, hallucinatory behavior, unusual thought content, and excitement. Negative symptom subscales were emotional withdrawal, motor retardation, and blunted affect.