BACKGROUND We investigated the effects of methylene blue (MB) on the early and late phases of adhesion and abscess formation in a standard colonic wall injury and fecal peritonitis model in rats. METHODS There were four groups: Group I (only laparotomy, n=10), Group II (peritonitis + MB, n=15), Group III (peritonitis + saline, n=15), and Group IV (colon incision + saline, n=15). Mortality, morbidity, adhesion scores, histopathologic analyses, serum tumor necrosis factor-alpha (TNF-α) levels, and tissue hydroxyproline (5-HP) levels were evaluated in all animals. Descriptive statistical methods were used with Kruskal-Wallis test. When a statistical difference was obtained between groups, Mann-Whitney U test was used to confirm the difference between two groups. RESULTS Adhesion scores of Groups I, III and IV were significantly higher than in Group II. TNF-α levels were significantly higher in Groups I, III and IV. 5-HP levels were significantly lower in Groups I and II compared to Groups III and IV. CONCLUSION Based on these results, it appears that MB may prevent peritoneal adhesions in a peritonitis model, but wound healing could be impaired. MB should be further evaluated because of its dual effect.