The authors retrospectively reviewed the plain films of 453 surgically proven cases of acute appendicitis, and compared the frequency of several radiographic findings of complicated(n=234) cases to that of uncomplicated(n=219) ones. We found that frequency of radiographic findings in complicated cases is much more common than that in uncomplicated cases: diffusely increased small bowel gas(85.3% vs 24.8%), air fluid level I right lower quadrant(RLQ)(47.0% vs 9.4%), soft tissue mass shadow in RLQ(15.5% vs 0.4%), and appendicolith(5.5% vs none), respectively. Although these plain film findings are not diagnostic perse, they may be helpful in discriminating the complicated cases from the uncomplicated ones.