Onychomycosis is a fungal infection of the nails, more often of the toenails. It is a common condition, with an estimated overall prevalence of 3–10% in European populations. Dermatophytes, especially Trichophyton rubrum and Trichophyton mentagrophytes, are the usual pathogens. Some 50% of infected patients fail to seek medical advice. Medically confirmed onychomycosis should be treated. This recommendation is based on several disease-specific considerations: cosmetic and functional disability, lack of spontaneous remission, impairment of health and wellbeing in elderly patients and the need to reduce contamination in communal bathing places. Current treatments for onychomycosis include oral antifungal agents such as terbinafine (Lamisil®) and itraconazole (Sporanox®). They offer significantly improved rates of cure, shorter treatment regimens and a lower level of adverse events than was previously the case. Comparative studies have shown that terbinafine is more effective than griseofulvin, fluconazole or itraconazole in the treatment of this condition, providing a cure rate of 70–80% and an excellent tolerability profile. Terbinafine is also the most cost-effective agent. However, several problems remain that will provide future challenges in the treatment of onychomycosis, not least the consistent treatment failure rate of 20%. In many of these cases, surgery may need to precede drug therapy in order to maximise the prospects of clinical and mycological cure. In addition, duration of treatment also needs to be more closely adjusted to the individual case by prior identification of severity and extent of toenail infection, and combined oral and topical therapy also requires further investigation.