Seven patients with ulcer cancer are reported. Three were peroperatively, one of them also preoperatively, suspected of malignancy and showed carcinomatous infiltration of the gastric wall, penetrating deep into the subserous layer in all cases, and lymph node infiltration in two. These patients died of their cancer, respectively 1/2, 2 and 41/2 years after operation. Four patients showed peroperative gross signs of benign gastric ulcer. In 3 of the cases carcinoma, respecting the subserous layer, was found histologically in the excised ulcer. After subsequent radical surgery in 2 and biopsy from the site of ulcer excision in 1, carcinoma was not found in the specimens. In the fourth case an excised piece of a prepyloric ulcer on the posterior wall showed superficial carcinoma. After subsequent radical operation persistent carcinoma was found in the resected specimen at the site of the biopsy. The 4 patients are alive without signs of cancer, respectively 31/2, 5, 8 and 8 years after the operation. The series demonstrates that histological examination of excised gastric ulcers may lead to the diagnosis of a carcinoma, which has limited extension and good prognosis after operative treatment.