Objectives : This study was aimed at investigating the medical service utilization pattern of patients who use public medical aid compared to those who have health insurance. Methods : We selected every patient between the age of 18 and 69 who used public medical aid from January 1, 1999, to December 31, 2001, in Gwangju metropolitan city, South Korea. For comparison, a list of patients with health insurance was gathered for same period. Then the medical records of those who had been hospitalized for acute appendicitis were selected among both groups. Of those records, we compared the number of cases of ruptured appendicitis to cases of whole acute appendicitis in both groups. Regarding coding for ruptured appendicitis, International Classification of Diseases - 10 (ICD-10) was used. Multiple logistic regression was used as a statistical tool to determine the effectiveness of risk factors. Results : Even after adjusting for risk factors, such as age and sex, the proportion of perforation of acute appendicitis among public medical aid patients was found to be significantly higher than among insured patients. Conclusions : This comparative study on ruptured appendicitis among public medical aid patients and insured patients, indicates that the proportion of perforation of acute appendicitis could be an index showing that these types of patients utilize medical services differently than insured patients. We know that when abdominal pain is not properly treated at the outset, it easily develops into ruptured appendicitis complicated with peritonitis. Considering this data analysis, we guess the public medical aid system to have significant problem with medical accessibility. So additional and systematic research on the pattern of utilization of medical services of public medical aid patients is needed.