There are few reports regarding the treatment of nail psoriasis with topical calcipotriol. We undertook a case series study to evaluate the efficacy and safety of calcipotriol ointment (50 microg/g) in the treatment of nail psoriasis in 24 patients. This study involved 19 women and 5 men with nail psoriasis referred to Dermatology clinics of Razi hospital. The duration of trial was from October 2002 to September 2004. Informed consent was obtained from all patients before entering into the study. The patients applied calcipotriol ointment to the affected nails twice daily without occlusion for 3 months. Patients were seen by two academic dermatologists initially, after 2 weeks, and then at monthly intervals. The efficacy and safety were clinically assessed and any side effect was recorded. Patients who showed 50 percent or greater reduction in the baseline subungual thickness in at least one nail were considered to be responders and were offered continuation of therapy for an additional 2 months. After discontinuation of therapy, followup visits were performed at 1 and 2 months. After 3 months of therapy, fourteen patients showed significant clinical improvement, two of them were completely free from nail lesions after 5 months. Calcipotriol was particularly effective in subungual hyperkeratosis, onycholysis, and discoloration. In four patients fingertip tenderness and in one case the pain of involved distal phalanx were significantly reduced. No clinical response was observed in four patients. Only two cases showed adverse reactions. Topical Calcipotriol is an effective treatment for nail psoriasis and can be considered to be a safe topical treatment in chronic cases; its high tolerability allows prolonged usage without severe side effects.