OBJECTIVE to evaluate the effects of arginine on abdominal wall healing in rats. METHODS we submitted 20 Wistar rats to laparotomy and divided them into two groups, arginine and control, which then received, respectively, daily intraperitoneal treatment with arginine (300mg/kg/day) and weight-equivalent phosphate buffered solution, during five days. On the seventh postoperative day, we collected blood and scar wall samples from both groups. We evaluated serum nitrate and nitrite levels, wound evolution by tissue hydroxyproline dosages, granulation tissue formation, percentage of mature and immature collagen, myofibroblast density and angiogenesis. We used the ANOVA and the Student's t tests with p=0.05 for comparisons between groups. RESULTS there were no significant differences between the groups studied for nitrate and nitrite (p=0.9903), tissue hydroxyproline (p=0.1315) and myofibroblast density (p=0.0511). The arginine group presented higher microvascular density (p=0.0008), higher percentage of type I collagen (p=0.0064) and improved granulation tissue formation, with better angiofibroblastic proliferation rates (p=0.0007) and wound edge reepithelization (p=0.0074). CONCLUSIONS in the abdominal wall healing evaluation of Wistar rats under arginine treatment, there was no change in serum nitrate and nitrite levels, total collagen deposition and myofibroblast density. There was an increase in type I collagen maturation, microvascular density and improvement in scar granulation tissue formation by better edge reepithelization and angiofibroblastic proliferation.