In order to determine the factors affecting the length of stay by pay status, a total of 961 in-patients medical records with appendectomy. cholecystectomy and Cesarean section discharged from the January 1979 to December 1981 from the University hospital were reviewed. Average length of stay showed no statistically significant difference by year between the insured and the non-insured patients, however multiple diagnoses and surgical complication were significantly different from single diagnosis and non-complicated cases. Surgical complication explained the length of stay mostly, and physician in discharge, multiple diagnoses, and accommodation in order for insured patients. Surgical complication, admission route, physician in charge and age in order explained the length of stay for non-insured patients.