The nail is commonly involved in psoriasis; however, very few therapies are satisfactory. In this study, we treated for 20 cases of psoriasis vulgaris with nail involvement with topical anthralin therapy. An ointment of 0.4-2.0% anthralin in petrolatum was applied to the affected nail bed once a day and washed away with water after 30 minutes. Then, 10% triethanolamine cream was applied to prevent undesired pigmentation. Within five months of therapy, twelve out of twenty psoriatic patients (60%) showed moderate and obvious improvement, four patients (20%) showed no response to this regimen. Onycholysis and pachyonychia both responded clinically, and the number of pitting was markedly decreased in some cases. The main side effect of anthralin therapy was reversible pigmentation of the nail plate. Topical anthralin therapy is effective for nail psoriasis and considered to be a useful treatment for refractory nail psoriasis.