The authors analyse the results of endoscopy in 127 patients and clinical observations over 98 patients with giant ulcers of the stomach. The study provided evidence of the low frequency of giant ulcers, their marked polymorphism, and tendency to bleed and degenerate. These ulcers do not differ from the usual ulcers in the values of the secretory activity of the stomach and the duodenogastric reflux, but possess characteristic morphologic criteria. Giant ulcers are marked by higher operative mortality and the late-term results of surgical treatment of these patients yield to those in cases of usual gastric ulcers. Giant ulcers occur most frequently in the elderly.