Ninety-one patients with acne vulgaris were selected for a two-part study primarily because the severity of disease suggested that it might be tetracycline-recalcitrant. Of the eighty-eight patients completing the first part of the study, thirty-two were judged to have tetracycline-nonresponsive acne and received 50 mg of minocycline twice daily for the next six to eight weeks. Twenty-five patients completed this second part of the study. Of these twenty-five, twenty-two experienced a 33 percent or greater reduction in the number of lesions. It is concluded that minocycline in a dosage of 50 mg twice daily is a safe and effective antibiotic for those patients with tetracycline-recalcitrant acne vulgaris.