Elective laparoscopic cholecystectomy is established as the treatment of choice for symptomatic cholecystolithiasis and is now proposed for the treatment of acute cholecystitis. The aim of this study is to evaluate biochemical aspects of open (OC) and laparoscopic cholecystectomy (LC. We measured the levels of malondialdehyde (MDA) and the levels of nitrite+nitrate as stable end products of nitric oxide (NO). MDA and nitrite+nitrate levels were increased at both surgical procedures compared to preoperative period, but the rise was more significant in OC than LC. These results showed that both OC and LC caused an increase in oxidative stress. However LC caused significantly less oxidative stress and the changes during surgery returned to preoperative values after LC in a shorter period. The beneficial effects of laparoscopic surgery may be related, partially, to less oxidative stress in the immediate postoperative period.