This paper reports the results of a multicenter prospective study of 188 consecutive patients affected by gastric ulcer, verified by endoscopy, in whom the frequency of a mycotic infection of the lesion was evaluated as well as the eventual influence of such pathology on the efficiency of medical treatment, the healing rate, and the healing time. A mycotic infection, defined as penetration of the periulcerous mucosa by the fungi, was found in only 13 patients (6.9%). No significant differences were found in the healing rate and healing time among these patients treated with H2-receptor antagonists and a control group of 43 matched gastric ulcer patients treated in the same period with the same therapy. It would appear from the data that mycotic infections of the gastric ulcer do not modify the efficiency of medical treatment.