In 46 patients with alopecia areata, one side of the head was treated with weekly applications of DNCB, dissolved in acetone. The therapeutic aim was mild contact dermatitis. The other side of the head served as control region. A therapeutic effect was noted in 36 patients: 22 patients showed regrowth of hair exclusively on the treated side, and in 14 patients regrowth of hair was considerably faster and more dense on the treated side. In 8 patients no regrowth was observed, and in 2 patients regrowth occurred on both sides without any difference of intensity. The difference between both sides with regard to hair growth was seen in all of the 7 patients with moderate involvement and in 12 out of 13 patients with extensive involvement; but also in 17 out of 26 patients with alopecia areata totalis or fere totalis. The difference was noted, in the majority of cases, within 3 months. These results prove the efficacy of DNCB treatment of alopecia areata.