Cyclosporine increases the risk of skin and lymphoid tissue malignancies in organ transplant patients. A similar increase has been shown among psoriasis patients, but no data exist on the carcinogenic risk of cyclosporine monotherapy in skin diseases. We conducted a retrospective cohort study of 272 patients, all of whom had received at least one month of cyclosporine treatment. The cancer information on these patients was obtained from the Finnish Cancer Registry. The median follow-up time was 10.9 years and the median treatment time with cyclosporine was 8 months. We did not detect any increase in the risk of skin malignancies or lymphoma. The overall risk of cancer was almost identical to that expected in the general population (standardized incidence ratios (SIR) = 1.31, 95% confidence interval (CI) = 0.70-2.23). This study shows that short-term cyclosporine treatment is probably not related to subsequent malignancy. Since the CI of the SIR estimate was rather wide, larger studies are needed in the future.