The effect on gastric epithelial cell proliferation of a short-term, low-dose treatment with aspirin was evaluated in 9 healthy volunteers. Nine days before and during aspirin administration, the subjects assumed sulglycotide, a sulfated glycopeptide with cytoprotective properties. Endoscopic biopsies were collected in each subject from the gastric body and antrum before and after treatment. The specimens were incubated in a culture medium containing bromodeoxyuridine (BrdU). The proliferative activity was evaluated by immunohistochemical detection of BrdU uptake. A decrease in BrdU-labelled cells together with a shortening of the length of gastric columns were observed after treatment with aspirin and placebo in biopsies of both body and antrum (p less than 0.05). On the contrary, no modifications were observed after treatment with aspirin and sulglycotide. We conclude that a decrease in the proliferative activity of the epithelial cells could be one of the mechanisms by which aspirin affects the defensive properties of gastric mucosa. The treatment with a cytoprotective drug seems to be effective in preventing this alteration.