Terbinafine, an allylamine derivative, represents the most effective of this new chemical class of antimycotic compounds. Under in vitro conditions, terbinafine proved to be highly active against dermatophytes (MIC range, 0.001 to 0.01 microgram/ml), aspergilli (MIC range, 0.05 to 1.56 micrograms/ml), and Sporothrix schenckii (MIC range, 0.1 to 0.4 microgram/ml) and also exerted good activity against yeasts (MIC range, 0.1 to greater than 100 micrograms/ml). The growth of Malassezia furfur was inhibited also (MIC range, 0.2 to 0.8 microgram/ml). Terbinafine displays a primary fungicidal action against dermatophytes, other filamentous fungi, and S. schenckii. The type of action against yeasts is species dependent and can be primarily fungicidal (Candida parapsilosis) or fungistatic (Candida albicans). The in vitro activity of terbinafine is pH dependent and rises with increasing pH value.