In 50 patients with benign gastric ulcer (eight relapsing, 42 nonrelapsing) the evolution of the edge and scar histological characteristics was studied with special regard to the pressure and modification of epithelial dysplasia. The patients were endoscopically followed-up; for 1 to 74 months. Dysplasia was present in 29% of observations made in active ulcer and in 19% of patients with scarring gastric ulcer. Severe dysplasia was found only in one case. During follow-up, regression of the dysplastic changes was documented in 64% of the cases, progression from mild to moderate dysplasia in 4%, while no change was recorded in 32%. Appearance of dysplasia or progression from mild to moderate was seen in 62% of the relapsing cases, as opposed to 14% of the nonrelapsing cases (p less than 0.005). Dysplastic changes, usually mild, are relatively frequent in the mucosa both at the edge and scar of gastric ulcer, but they tend to disappear with the healing of the ulcer. Appearance or progression in severity of dysplasia during follow-up are rare, but significantly more frequent in relapsing ulcers, which therefore require more careful follow-up.