One hundred thirty-nine patients with alopecia areata were treated with diphenylcyclopropenone. Before treatment, 85 patients had subtotal or total hair loss (greater than 90% bald area) and in the remaining patients scalp involvement was between 40% and 90%. The following three factors were found to be of prognostic significance: type of alopecia areata as documented before treatment, duration of the disease before therapy, and presence of nail changes. Other factors such as age at onset, sex, presence of atopic features, the extent of variation in the range of diphenylcyclopropenone concentrations during treatment, and sleep disturbances caused by pruritus did not influence the prognosis significantly.