The controversy about the risk of cancer in patients surgically treated for peptic ulcer is debated in the literature. We analyzed published epidemiological studies, in an attempt to answer the following questions: 1) is there an increased risk of cancer in patients who underwent partial gastrectomy for ulcer disease?; 2) is such a risk influenced by the type of operation performed and by the original pathological lesion?; 3) are there any recommendations for peptic ulcer surgery and for a specific follow-up schedule of the patients? Twelve "prospective" studies have been published on patients operated on for peptic ulcer. These studies are based on the follow-up of a cohort over a certain period of time. Results are expressed and analyzed using the incidence ratio observed in the cohort, comparing observed with expected cases in a similar general population. The results of seven of these studies favor the hypothesis of an increased risk of stomach cancer in patients operated on for peptic ulcer disease, while those of five do not support this hypothesis. The results of two of these studies were obtained by multivariate analyses, which represent the best statistical methodology known for assessing the respective role of confounding variables. We therefore believe that the evidence is good enough to identify patients who underwent partial gastrectomy more than 20 years previously as a high-risk group for the development of carcinoma. We therefore recommend that these patients should be offered regular endoscopy, especially if they underwent a Billroth II surgical procedure.(ABSTRACT TRUNCATED AT 250 WORDS)