5 patients with alopecia areata were treated with local application of DNCB in acetone over a period of 3–9 months. 9 of these had alopecia areata totalis, 3 had alopecia areata fere totalis, and 3 had common alopecia areata. The results are comparable with those of other authors. The response did not depend upon the duration of the disease but upon its extension. In all patients with alopecia areata and alopecia areata fere totalis, hair growth was induced, while only 2 of the 9 patients with alopecia areata totalis responded satisfactorily. One third of the latter were children in whom the treatment may be less effective than in adults. Contact allergy was induced in all but 1 case in which no hair growth occurred. Since the mutagenic effect of DNCB has been demonstrated in the Ames test, DNCB ought to be replaced by other haptens, but its possible cancerogenic effect must be tested in other in vivo model