Cellular and humoral immune parameters were studied in 10 patients with alopecia areata totalis and universalis. Trends to low normal immunoglobulin levels and in vitro lymphocyte transformation to concanavalin A were observed. Serum CH-50 levels and skin test responses to mumps, Candida, trichophytin and dinitrochlorobenzene (DNCB) were normal, as were the numbers of T and B cells. Immunosuppressive serum factors were not found in vitro. 1 patient with alopecia universalis of 33 years duration developed hair at the site of DNCB skin testing. The findings point to rather subtle immune defects in patients with this disease.