Stress is known to induce gastric ulcerations but the mechanism of their healing has been little studied. This paper describes the studies on mucosal expression and the effect on ulcer healing of spasmolytic peptide (SP), one of the members of the trefoil peptide family. Gastric ulcerations were induced in rats by the exposition to 3.5 h of water immersion and restraint stress. It was found that the number of these lesions gradually declined at 4, 8 and 12 h after stress and this spontaneous healing was significantly accelerated by s.c. infusion of human recombinant SP in a constant dose of 50 micrograms kg-1 h-1. The healing of the stress-induced ulcerations was accompanied by a gradual restoration of gastric mucosal blood flow and the decrease in gastric acid and pepsin secretion towards the normal values. The expression of SP in rats (rSP) was detected by RT-PCR in the intact mucosa and during all tested time periods reaching a peak at 4 h after the stress. Immunostaining for rSP in the intact mucosa was confined to the mucous neck cells, but following the exposure to stress it was significantly enhanced and occurred also in the cells of the basal region of gastric glands, reaching a peak at 4 h after the stress. We conclude that SP plays an important role in healing of stress-induced gastric lesions possibly by the acceleration of the mucosal repair, the enhancement of mucosal blood flow and the inhibition of gastric secretion.