A clinical trial involving 100 duodenal ulcer patients was performed at the Shiraz Medical School in Iran, in which the known risk factors that influence the healing of duodenal ulcers in West Germany were examined. The patients were randomly allocated to groups receiving 2 x 400 mg cimetidine daily for 10 days (group I) or 28 days (group II). In addition, antacid was taken if pain occurred. Probable prognostic risk factors were noted, such as: age, sex, duration of ulcer history, duration of the present ulcer relapse, smoking habit, nocturnal pain, radiation of pain to the back, history of ulcer bleeding and use of analgesics. The number of ulcers, ulcer size, ulcer depth, bulbar deformity and narrowing were determined endoscopically. Follow-up examinations were performed in 89 patients 4 weeks after the start of treatment. The ulcers were healed in 20 out of 43 patients in group I (46%), and in 29 out of 46 in group II (63%) (p = 0.11). Statistical analyses were performed in both group combined to investigate unfavorable factors for healing. Following univariate analysis the following factors were prognostically unfavorable: bulb deformity (p = 0.003), radiation of pain to the back before treatment (p = 0.045), number of cigarettes smoked per day (p = 0.046). The patients with non-healed ulcers had more days with pain during treatment (p = 0.045). Using logistic regression analysis, the following prognostic factors were significant: number of cigarettes smoked per day (p = 0.03), radiation of pain to the back (p = 0.036), and bulb deformity (p = 0.048).(ABSTRACT TRUNCATED AT 250 WORDS)