Cocaine is a potent topical vasoconstrictor that causes nasal mucosal and dermal ulceration. Use of the purified cocaine derivative "crack" has reached epidemic proportions in large cities. In 18 months we operated on 24 patients with perforated peptic ulcers. Five of the patients were young (27-38 years) male crack users without prior history of gastric symptoms who presented with a perforated gastric ulcer related to smoking crack. Three had had symptoms for only 1-5 days before admission. All five were afebrile, had a rigid abdomen, normal leukocyte count, and free intraabdominal air upon radiography. Five other age-matched, non-crack-using patients served as case controls. Their duration of symptoms was 1-24 months, they had elevated leukocyte counts on admission, and, in contrast to the crack users, four of these patients had duodenal perforations. The clinical presentation of the crack smokers and the unusual localization of the perforations imply different pathogenetic mechanisms than are commonly seen in perforated ulcer disease. With increasing abuse of crack, greater numbers of patients with this new complication may be expected to present to emergency services in urban areas.