Ninety-four patients with inflammatory acne were treated with demethylchlortetracycline hydrochloride in a doubleblind, modified, crossover study. Good to excellent responses were obtained in 58% of the patients receiving demethylchlortetracycline, and in 24% of those receiving placebo. The drug, when used in a dosage of 150 mg three times daily without concomitant therapy, primarily affected inflammatory papules and pustules. Response to treatment was determined by counting lesions on the involved sites.