Many systemic factors may influence the healing process. The present study aimed to analyze histological modifications induced by the presence of Ehrlich ascites tumors on laparotomic surgical scars in BALB/c mice. A total of 52 mice were used. Half of the mice were injected with Ehrlich tumor cells, and 7 days later (day 7) all mice underwent laparotomy. On day 11, the scar was resected in 10 mice with the tumor and in the 10 control mice. The procedure was repeated on day 14 with the remaining animals. The scar tissue was histologically evaluated by means of semiquantitative analysis for acute inflammation, re-epithelization, formation of granulation tissue, chronic inflammation, fibroblast proliferation, and collagenization. Mice injected with tumor cells gained weight due to ascites growth. Histologic results showed that Ehrlich ascites tumor cells did not affect initial acute inflammation, re-epithelization, and formation of granulation tissue (P = ns). Chronic inflammation and fibroblast proliferation were, however, significantly decreased in mice with tumors, whereas collagenization had increased (P = 0.001). These results show that Ehrlich ascites tumors affect the healing process in mice. Despite a decrease in chronic inflammation and fibroblast activity, scars in these animals had more collagen, were more fibrous, and were better organized. .