Most clinical studies in subjects with toenail onychomycosis end with a final assessment at 48-52 weeks. This fails to take full account of the physiology of toenail growth, as toenails can take up to 12-18 months to grow out fully. Accurate assessment of long-term outcomes therefore requires follow-up of at least 2 years after completion of the study. We have evaluated long-term outcomes of treatment in the patients whom we contributed to two multicentre studies of oral therapy for toenail onychomycosis caused by dermatophyte infection. In the first, a dose-finding study for terbinafine (Lamisil), the high rates of mycological and clinical cure achieved by terbinafine at week 48 were maintained more than 2 years after completion of the study. In the second, a comparative study between terbinafine and itraconazole (Sporanox), the excellent mycological and clinical cure rates achieved by terbinafine at week 48 were again maintained more than 2 years after completion of the study. By contrast, the failure and relapse rates seen with itraconazole were much higher. Other studies undertaken in recent years have confirmed these positive findings with respect to terbinafine, and have demonstrated its superiority over itraconazole in maintaining mycological and clinical cure over long periods. These long-term benefits of terbinafine probably relate to its primarily fungicidal action against dermatophytes, compared to the fungistatic action of itraconazole and other triazole agents. Future clinical studies should therefore incorporate at least 2 years' follow-up.