Polymorphonuclear leukocytes (PMN) are well recognised as being the principal cells in the inflammatory response reaction. The current investigation was designed to evaluate the stimulated state of neutrophils in patients undergoing open (OC) and laparoscopic cholecystectomy (LC). The superoxide radical generation of isolated PMN and its lag time, and PMN elastase were measured in peripheral venous blood samples collected from 42 patients. The observation period started on the day of hospital admission and ended on the 5 th day. Our results showed that although there were no characteristic changes in the superoxide radical production of PMN in the LC group, we found a marked depletion already by the first day in OC group which persisted during the whole observation period. There was an elevation of PMN elastase on the first postoperative day in both groups, but in the laparoscopically operated patients it decreased considerably on the 3rd postoperative day while in the OC group it maintained a high level. The same discrepancy was present between the two groups on the 5th day. Decreased free radical production of isolated PMN may reflect depleted neutrophil functional state, while changes of PMN elastase indicates increased harmful potential. These data suggest the differences in neutrophil activation between the two groups can be partially responsible for the better outcome in patients operated by laparoscopic cholecystectomy.