As calcipotriol has been reported to increase mitotic activity, to have a role in regulating immune response and to increase the contact hypersensitivity response when applied topically at the elicitation site we sought to determine whether topical calcipotriol is able to potentiate the response to squaric acid dibutylester (SADBE) in severe alopecia areata. A group of 28 subjects with severe alopecia areata were sensitized with a 2% SADBE solution applied to the vertex. After 2 weeks and then weekly, a 0.001% SADBE solution was applied to the whole scalp. Every day, except the day of SADBE application, an ointment containing 50μg/g calcipotriol was applied to the left side of the scalp. Treatment with calcipotriol and SADBE did not significantly potentiate hair growth (P= 0.133). This study suggests that calcipotriol has an inhibiting action on cell multiplication.