A prospective, randomized, double-blind study on the effect of cephaloridine prophylaxis in the surgical management of appendicitis was performed. Of the 139 patients studied, 70 received cephaloridine and 69 received placebo prophylaxis. Both groups of patients were well matched with regard to age, sex, operative findings, and bacteria isolated at operation. Postoperative wound infections were detected in 11.6% of placebo-treated patients and in 1.4% of cephaloridine-treated patients (P less than .02). Prophylactic treatment with cephaloridine of patients undergoing surgery for uncomplicated appendicitis resulted in a perceptible reduction in the rate of postoperative wound infection.