A randomized, prospective, double-blind study designed to compare the effectiveness of the use of cloxacillin with the result of nontreatment in patients undergoing surgical intervention of axillary hyperhidrosis was conducted from August 1987 to October 1987 at the Veterans General Hospital, Taipei, Taiwan. Forty-two patients were enrolled in this study. Fifty wounds (25 patients) were control subjects, and 34 wounds (17 patients) received cloxacillin. The positive bacterial culture rates of the tissues and draining from patients in the treatment group compared with the control group was statistically significantly lower (p less than 0.01). No significant differences presented in relation to age, sex, complication rate, fever index, and length of hospital stay. Prophylactic antibiotic is of no value in elective surgical intervention of axillary hyperhidrosis.