BACKGROUND: The current study evaluated the effect of time in the severity of the oxidative stress due to pneumoperitoneum.METHODS: Forty Wistar rats were allocated randomly into 2 groups. The 1 h pneumoperitoneum (Pp) group, which was subjected to 60 min of pneumoperitoneum, and the 3 h Pp, to pneumoperitoneum for 180 min. The animals were divided in half. One half of the rats were left resting for 30 min after abdominal desufflation and the other for 8 h. After these two time periods, blood, liver, kidney, lung and small intestine were obtained for biochemical analysis and histopathological examination.RESULTS: In the 3 h Pp, the associated oxidative stress was increased. There was an overt increase in blood and tissue MDA and blood PAB values. The MPO values were significantly higher in the 3 h Pp group in serum, kidneys, and intestine during the early phase of reperfusion and in liver after 8 h of reperfusion. These changes occurred in the presence of light microscopic evidence of greater tissue damage for the 3 h Pp, which were consistent with the fluctuation of the MPO values.CONCLUSION: In our experimental model, we proved biochemically and histologically that time of maintenance of pneumoperitoneum is an additive factor that could cause increased oxidative stress in laparoscopic procedures.