Endoscopic distinction between ulcers and erosions is difficult. Consequently, existing literature, which must be taken at face value, may be misleading. Nevertheless, from published studies most gastric and duodenal ulcers associated with nonsteroidal antiinflammatory drugs appear to heal on antacids or H2-antagonists. Sucralfate appears useful for duodenal but not gastric ulcers. Continuing nonsteroidal antiinflammatory drugs does not prevent or delay healing of duodenal or small gastric ulcers; their effects on large gastric ulcers remain uncertain. Thus far, only full doses of H2-antagonists, or their combinations with antacids, have been shown to heal ulcers and prevent recurrences. Ulcer recurrences and complications have occurred in small numbers of patients on maintenance doses of H2-antagonists. Available antiulcer drugs (antacids, H2-antagonists, sucralfate) reduce severe acute injury when taken before or with nonsteroidal antiinflammatory drugs. They also reduce ulcerlike symptoms due to nonsteroidal antiinflammatory drugs. Inexplicably, chronic prophylaxis with H2-antagonists for 4 wk or more appears ineffective in preventing gastric ulcers, although duodenal injury is reduced. As the efficacy of available prophylactic therapy (H2-antagonists, sucralfate, and antacids) has not been established, routine use in all cases seems unjustified at present.