This study examined effects of acute doses of phencyclidine (PCP; 0.025, 0.05, 0.10, and 0.20 mg/kg intraperitoneally) on intra-specific aggressive behavior and muricide in normal rats and rats deprived of rapid eye movement (REM) sleep. Dose-related changes in intra-specific aggression and muricide occurred in REM sleep-deprived rats only. Dose-response curves are inverted-U shaped with the .05 mg/kg dose producing increases in aggression. Intra-specific aggression and muricide may serve as models of PCP-induced aggression in humans.