Forty-five patients with extensive alopecia areata were treated by local application of diphencyprone. Only eleven had satisfactory regrowth of hair. Six had moderate regrowth, and of the remaining 28 some showed regrowth ofvellus hair and others had no response. The side effects of the treatment consisted of intense allergic or irritant reactions, febrile reactions, anaphylactic reaction with fainting, and vitiligo. In twelve patients progressive desensitisation was observed. As the effectiveness of this treatment is low and side effects are common and sometimes severe, we conclude that diphencyprone has no advantage in the treatment of alopecia areata.