To establish a primate animal model of schizophrenia with negative symptoms, the behavioral effects of chronic phencyclidine (PCP) and additional acute methamphetamine (MAP) administration were investigated in six monkeys. The results indicate that chronic PCP treatment induced a significant decrease in all categories of social behaviors, and that the chronic PCP monkeys also spent less time in proximity to other monkeys than the control monkeys. Acute MAP injection to the chronic PCP monkeys exacerbated the behavioral effects of PCP. The results suggest that these monkeys can be used as a primate model of schizophrenia with negative symptoms.