Tumor necrosis factor alpha (TNF-alpha) phenotypes of two polymorphic systems were determined in 50 patients with alopecia areata, a common inflammatory disease of the skin. The distribution of TNF-alpha T1, T2 phenotypes differed between patients with the patchy form of disease and patients with totalis/universalis disease. There was no significant difference in the distribution of TNF-alpha G,A phenotypes between patient groups. The results of this study provide evidence of genetic heterogeneity between the two forms of alopecia areata, and suggest that the TNF-alpha gene or a closely linked locus within the major histocompatibility complex may play a role in the pathogenesis of the patchy form of disease.