Onychomycosis is a common nail infection for which treatment options are limited, and no new treatment have been introduced for over 10 years. While patients might prefer a topical therapy, efficacy with ciclopirox and amorolfine lacquers has been disappointing especially in moderate to severe disease. Efinaconazole 10% solution is a new triazole antifungal, specifically developed for the topical treatment of onychomycosis. Its physicochemical properties, antifungal activity and formulation are all important aspects of the development program and are reviewed here. Efinaconazole 10% solution may provide the first viable alternative to oral therapy for onychomycosis. Mycologic cure rates are comparable to those seen with oral itraconazole, and greater than reported with ciclopirox lacquer. © 2013 Informa UK Ltd.