In this prospective study the free radical mediated reactions, the changes of endogenous antioxidant defense mechanism and activation of leukocytes were measured from the blood of patients undergoing elective cholecystectomy because of symptomatic cholecystolithiasis. The patients were randomised into two groups. Group one contained 21 patients treated by open cholecystectomy(OC). Group two consisted of 21 patients treated by laparoscopic cholecystectomy (LC). Both groups had similar patient characteristics. Patients with acute cholecystitis, pancreatitis, choledocholithiasis or other disease were excluded. Values from patients in both groups were compared. The measured biochemical parameters are the following: malondialdehyde (MDA) as a marker of the free radical induced lipid peroxidations, reduced and oxidised glutathione (GSH-GSSG), as endogenous scavengers as well as markers of oxidative stress and myeloperoxidase activity (MPO) of leukocytes. The results showed significantly lower values of postoperatively measured MDA, GSH-GSSG, and MPO activity of leukocytes in patients with laparoscopic cholecystectomy, indicating a lesser stress response and tissue trauma in this group of patients. The results correspond to the favourable results of most other trials evaluating clinical aspect of LC.