One hundred and five patients with gastric erosion were followed up gastroscopically. In 69 patients (66%) the lesions healed in a mean of 0.9 +/- 1.1 (SD) years, but in 36 patients they persisted for a mean follow-up time of 3.1 +/- 1.7 years. In the patients with incomplete erosions on the prepyloric folds the lesions healed in 38% of the cases, and the mean healing time, 2.4 +/- 1.9 years, was statistically significantly longer than that for the other types (p less than 0.02). The erosions were oftener chronic in men than in women (p less than 0.01). Peptic ulcer developed in four patients. Foveolar hyperplasia in the mucosa developed in the patients with complete erosions (p less than 0.01) and achlorhydria (p less than 0.001). Two additional cases of polyps were observed among patients with complete erosions and achlorhydria. No malignant changes occurred. The acid secretion capacity was higher in the patients with unhealed erosions (p less than 0.005). The use of analgetics was common in the patients with unhealed erosions (p less than 0.01).