Treatment of nail psoriasis is difficult. Several topical therapies have been employed with poor results because drug penetration is limited in this localization. Recently, a new formulation containing 8% clobetasol-17-propionate in a colourless nail lacquer vehicle has shown good results in the control of nail psoriasis. To determine the efficacy and safety of 8% clobetasol-17-propionate in a lacquer vehicle in nail psoriasis. Ten patients with both nail bed and matrix psoriasis were included in the study. They were treated with a colourless nail lacquer containing 8% clobetasol-17-propionate that was applied once daily for 21 days and then twice weekly for 9 months. Within 4 weeks of therapy there was a reduction of all the nail alterations, including nail pain. Therapeutic response was directly related to the length of therapy. The nail parameters that responded best to therapy were onycholysis, pitting and salmon patches. Subungual hyperkeratosis and splinter haemorrhages on the other hand had moderate and poor improvement, respectively. The treatment was well tolerated in all of the patients and there were no local (i.e. atrophy and sobreinfection) or systemic secondary effects. The formulation containing 8% clobetasol-17-propionate is a safe, effective and cosmetically highly acceptable treatment for nail bed and matrix psoriasis.