Comedones and closed comedones were extracted unilaterally from the foreheads of 20 patients and from the cheeks of 12 patients with acne vulgaris. Subsequent comparison of treated and untreated sides showed that this procedure was effective in most patients in preventing the development of inflamed acne lesions when applied to the forehead and when applied to other areas in patients with very superficial forms of acne. The procedure was rarely of value in cystic acne.