One hundred and forty-four patients with apparently benign gastric ulcer were endoscopically followed up in order to evaluate the outcome of the lesion. Particular attention was given to: (a) detect possible delay in diagnosing gastric cancer; (b) ascertain the frequency of association with epithelial dysplasia; (c) establish the role of markers, such as serum pepsinogen group I (PGI), and gastric juice CEA in predicting gastric ulcer evolution. Endoscopic and bioptic check-ups were carried out during the first year at 3, 6 and 12 months after endoscopic healing of the ulcer, and then at every symptomatic recurrence. Ten patients (6.9%) were found to present histological evidence of malignancy (within 3 months in six cases, between 6 and 12 months in three cases, and after 41 months in the rest). Four cases were early gastric cancers, and six had shown dysplastic changes of the mucosa at the edge or scar of the ulcer. Serum PGI levels were not significantly different in gastric cancer patients, while gastric juice CEA levels were sharply increased compared to those of gastric ulcer patients: nine out of ten patients had values above normal range. These data suggest that: (a) there may be some delay in diagnosing gastric carcinoma, and gastric ulcer patients should be controlled routinely more than once; (b) the presence of dysplasia indicates the need for prolonged follow-up, because of the high risk of association with or evolution into gastric cancer, and because of the higher number of early gastric cancer detections that this protocol allows; (c) further support in monitoring patients "at risk" may be afforded by gastric juice CEA determination.