The authors report on the incidence of tardive dyskinesia (TD) in a sample of 284 psychiatric patients who chronically abused street drugs; 82.4% had received neuroleptic treatment for the length of their illness (10.5±5.8 years). The incidence of TD was 15.9%. The incidence of TD was significantly higher in groups of patients in which alcohol alone (25.4%) or in combination with cannabis (26.7 %) was the drug of abuse than in those groups in which alcohol was either absent or used in combination with sedatives, opioids, or stimulants. Tardive dyskinesia was absent in patients not treated with neuroleptics and in a control group of drug abusers free of mental disorders. The anatomical distribution was similar to that reported in other psychiatric samples. Mean severity was mild and incapacitation and distress were minimal. Polydrug abuse was dominant in both patients and controls, and alcohol abuse was more