Violence associated with chronic phencyclidine (PCP) abuse was investigated by administering a structured interview to 16 chronic PCP abusers. A more intensive study was done of another individual who committed murder and self-mutilation under the influence of PCP. The results suggest that there is no consistent association between PCP-related violence and a history of violence not related to drug or alcohol abuse. The author defines four types of violence associated with chronic PCP abuse.