Objective To measure intestinal permeability of postoperative fasting patients and evaluate their intestinal barrier function.Methods Twenty patients after moderate or minor operation ,10 male and 10 female,were included in the study .After 3 to 5 days of fasting,when their bowel functon returned to normal,10 ml solution of lactulose(2g) with mannitol (1g) were given orally,urine of 6 hours was collected.As a control group,20 healthy volunteers were also included.There were no statistical differences in sex and age between two groups.Results The L/M of the patients and healthy volunteers were 0.1989?0.1186 and 0.4398? 0.2165 respectively,the difference was significant.Conclusions The intestinal permenbility of postperative fasting patients was elevated when compared with that of volunteers.