A simplified comedogenic assay is described in which test materials are applied for 2 weeks to the ears of rabbits just external to the ear canal. Excised tissue is thus immersed in water at 60 degrees C for 2 min, yielding a sheet of epidermis with microcomedones attached. The magnitude of follicular hyperkeratosis is extracted with the stereomicroscope. Sixteen materials were evaluated by the new and old model which required histological sectioning. Agreement was excellent.