Terbinafine (SF 86-327) is a new antifungal agent derived from naftifine and effective by the oral route. We studied the in vitro antifungal activity of terbinafine (SF 86-327) against several pathogenic fungi responsible for human disease. Tested pathogens included yeasts (Candida), dermatophytes (Microsporum, Trichophyton, Epidermophyton), molds (Aspergillus, Scopulariopsis) and dimorphic fungi (Sporothrix schenkii). Broth dilution (Sabouraud) or agar dilution (Sabouraud, Kimmig) were used. 322 strains of pathogenic fungi belonging to 23 different species were tested. The yeasts showed varying degrees of susceptibility (MICs ranging from 10 to 100 micrograms/ml) except for Candida parapsilosis (MICs 1 to 2 micrograms/ml). Strong susceptibility was found for molds (MICs 0.1 to 2 micrograms/ml), especially Scopulariopsis brevicaulis and Sporothrix schenkii (MICs 0.2 microgram/ml). Dermatophytes were also highly susceptible to terbinafine (MICs 0.001 to 0.02 microgram/ml).