Mycoses vary widely in severity, and may present as superficial, subcutaneous and/or systemic infection. Effective treatments for most superficial mycoses now exist, but new agents with convenient dosing regimens and a low level of adverse events are still needed to reduce morbidity and mortality from serious subcutaneous and systemic fungal infections. In vitro, terbinafine exhibits a broad spectrum of activity against the pathogenic fungi responsible for deep mycoses. Clinical data, while not abundant, suggest that this in vitro activity of terbinafine is reflected in its in vivo efficacy. The limited data show that terbinafine is a useful first-line treatment in chromoblastomycosis patients and has efficacy in pulmonary aspergillosis. There are also data to suggest that terbinafine may be effective in treating histoplasmosis, Pneumocystis carinii infection, fungal mycetoma, and cutaneous leishmaniasis. Moreover, there is some evidence of terbinafine having synergistic activity with amphotericin B, itraconazole, and fluconazole against clinical isolates of Candida species. Thus, the therapeutic potential of terbinafine extends well beyond its current use in acute and chronic dermatophytoses to include a wide range of subcutaneous and systemic mycoses. Studies are needed to determine the optimum dose in each disease, and whether combination therapy would have advantages in certain circumstances.