We performed a cost-effective evaluation of cyclosporin A versus UVAB phototherapy in the treatment of severe atopic dermatitis. The analysis was based on a one-year open prospective clinical trial conducted in Finland and showed that patients who received intermittent cyclosporin A therapy had on average 191 remission days per year, i.e. where disease activity was reduced by 50% or more. Patients receiving UVAB phototherapy had on average 123 remission days per year. All costs were estimated for the one-year period. Health service utilization of the 2 treatment groups was estimated based on the data gathered during the clinical study. Total costs were USD 5,438 in the cyclosporin A group and USD 5,635 in the UVAB group. Direct health-care costs were USD 4,935 in the cyclosporin A group and USD 3,124 in the UVAB group. The cost of a remission day was USD 28 in the cyclosporin A group and USD 46 in the UVAB group. In terms of direct health-care costs, the cost of a remission day was USD 26 in the cyclosporin A group and USD 25 in the UVAB group. Our results demonstrate that cyclosporin A therapy is similarly cost-effective as UVAB phototherapy in terms of total cost in the treatment of atopic dermatitis unresponsive to topical treatment. In terms of direct health-care costs, i.e. treatment and health services utilization costs, however, UVAB is significantly less costly, but side effects are frequent.