To reveal the aetiology and pathogenesis of chronic gastric erosions, selected clinical and laboratory variables in 117 patients with different types of gastric mucosal erosion as a predominant finding at elective gastroscopy were studied and the results compared with age- and sex-matched controls. Recurrent symptoms were the only characteristics in the symptomatology of the erosion patients compared with the controls (p less than 0.001). Recent ingestion of analgesics was associated with incomplete (type IIa) erosions (p less than 0.001) and was common especially among female patients. Irregular working hours were also reported by patients with this type of erosion (p less than 0.025). Smoking was more common among erosion patients than controls (p less than 0.05). Herpes labialis lesions (cold sores, fever blisters) occurred in 10 of the erosion patients, but in only one of the corresponding controls (p less than 0.01). Herpes simplex/virus antibody titres of 1:32 or more were associated with the erosions (p less than 0.05), particularly the complete (type I) ones (p less than 0.01). Thus, the various factors probably of importance in the aetiology and pathogenesis of gastric mucosal erosions are the same as those discussed in peptic ulcer disease, which points to a common aetiology and pathogenesis. The possibility of herpes simplex/virus aetiology in some, perhaps complete type, erosions is suggested.