Previously we showed that peptides PGP, PG, GP and semax have protective anti-ulcer properties using different models of ulcerogenesis. Semax (MEHFPGP) is a nootropic analogue of adrenocorticotropin 4-7 stabilized by PGP in the C-terminal region. In this study we examined the impact of these peptides on the development and healing of acetic ulcers in rats. The histomorphological and dynamical characteristics of acetic ulcers are most similar to human chronic ulcers. All the peptides were shown to accelerate the process of ulcer cicatrisation in a varying degree (GP semax PG PGP). The dynamics of structural changes in the place of ulcer formation investigated with the use of cytohistological control demonstrated that their anti-ulcer effects can be related to their ability to accelerate ulcer clarification from necrotic tissues and to activate the process of cicatrisation and epithelization. PGP and GP were also shown to reduce the inflammation in the ulcer zone on the fifth day after acetic acid application.