Over a period of 9 months we treated 50 patients with upper gastrointestinal bleeding from a peptic ulcer with a visible vessel. Their mean age was 58.8 years. Almost all cases had massive bleeding and required an average of 1930 +/- 2174 ml (S. D.) of blood. Twenty-eight cases were in shock when treated. The lowest mean hemoglobin was 8.2 +/- 2.2 gm/dl (S. D.). We treated them with the Olympus GIF-1T10 and the heat probe unit. A total of 825 +/- 735 joules (S. D. ) were applied to each bleeder. Forty-nine cases (98%) stopped bleeding after initial treatment. Seven cases (14.3%) rebled within one week post-treatment. We tried heat probe therapy again in 6 of the cases that rebled, and achieved hemostasis in four of them. Ultimately, only four failures were seen in our study. The success rate was 92% (46/50). We conclude that thermocoagulation with the heat probe may in the near future replace surgery in the majority of cases of hemorrhage from a peptic ulcer with a visible vessel in its base.