Alopecia areata is a human hair disease of unknown etiology. Immunological mechanisms, alterations in the extracellular matrix and follicular growth abnormalities have been suggested as a possible cause. Here we compare the expression of cytokeratins in normal hair follicles to that of alopecia areata using immunohistology with monoclonal antibodies. A number of cytokeratins were specifically expressed in defined anatomical parts of the follicle; however, no gross qualitative or quantitative differences were found between normal and diseased scalp. Interestingly, the expression of cytokeratin 16, which is modulated by conditions that affect the rate of keratinocyte proliferation, was found to be unchanged in the outer root sheet of alopecia areata follicles. This is in contrast with earlier observations of a decrease in the expression of the proliferation-associated, Ki-67 nuclear antigen.