The incidence and clinical characteristics of multiple or giant ulcers (over 20 mm for duodenal ulcer or 25 mm for gastric ulcer) was evaluated among 1434 patients with peptic ulcers. For gastric ulcers, multiple and giant lesions were found in 27% and 14% of patients respectively. Among duodenal ulcers the corresponding figure were 16% and 2.4%. Patients with triple gastric ulcers have a greater incidence of massive bleeding. Patients with triple duodenal ulcers are older, have more massive bleeding and have a greater incidence of gastric retention and hypersecretion when compared to patients with single or double duodenal ulcers. Giant gastric ulcer was associated to a shorter history and more massive bleeding; giant duodenal ulcer was associated to older age, more massive bleeding and gastric retention, when compared to patients with common size ulcers.