One hundred thirty-nine patients with severe alopecia areata (the majority with the subtotal, total, or universalis type) were treated with topical immunotherapy (diphenylcyclopropenone). Patients were initially treated unilaterally; the other side of the scalp served as a control. In 50.4% of the patients the response was either excellent (total regrowth) or satisfactory (subtotal regrowth with only a few remaining bald patches). The most frequent side effects were eczematous reactions with blistering, spreading of the induced contact eczema, and sleep disturbances.