In this study, anti-inflammatory, wound healing and anti-ulcerogenic properties of chitosan were evaluated ‘in vivo’ using wistar rats and swiss adult mice and the anti-proliferative activity was tested ‘in vitro’. The tested chitosans displayed no anti-proliferative or anti-inflammatory properties. The cytotoxic activity of chitosan was found to be non-existent towards eight tumoral cell lines and no significant differences were found in the ear edema (anti-inflammatory model) induced by croton oil and chitosan groups. However, chitosan showed good anti-ulcerative and wound healing abilities. Low molecular weight (LMW) chitosan effectively reduced ulcerative wounds induced by ethanol, while high molecular weight (HMW) chitosan helped retain the stomachal folds rendering a gastro protective effect. These results suggest that chitosan can potentially be used in the treatment of peptic ulcers. HMW chitosan also potentiated the healing process both in normal and diabetic rats, probably without induction of fibroblast growth but via collagen synthesis.