The aim of our study was to evaluate the clinical features, predisposing factors and pathogens of toenail onychomycosis in Estonia. During study period we interviewed and examined 436 dermatological patients with clinical signs of toenail onychomycosis in all counties of Estonia. In 69% of cases, the clinical diagnosis of onychomycosis was confirmed by the mycological analysis. The most common clinical symptoms of onychomycosis both in mycologically proven and non-proven cases were discolorization of nail plate, hyperkeratosis and brittle nails. The number of infected toenails positively correlated with patients' age. On average, patient had 5.4 infected nails. In 78% of culture-positive cases, a dermatophyte was isolated as the causative agent, in 10% yeasts and in 7% moulds. In 6% of culture-positive cases we reported mixed infections. Trichophyton rubrum was the most common pathogen. The high occurrence of mixed infections, clinical symptoms characteristic to long lasting or chronic infection and high number of infected toenails indicate that Estonian patients have more advanced stage of toenail onychomycosis compared with other western and central European countries.