We studied glyprolines influence on development and healing of acetate ulcers in rats. A maximal ulcer area has developed four days after application of acetic acid to gastric serous mucosa. Estimation of ulcer area in the control and experimental animals receiving a physiological solution or peptides was carried out on day 4 or 7 after ulcerogenesis. Single administration of PGP, PG or GP in an equimolar dose of 3.7 mcmol/kg (i/p) during 1-3 days after the application significantly reduced ulcers by 88%, 93% and 94%, respectively, compared to the controls. Administration of these peptides for 4-6 days after application led to a significant reduction of the lesions by 46,50 and 96%, respectively, vs controls. Thus, glyprolines inhibit development of acetic ulcers and enhance their healing.