The antifungal activity of 7-chloro-3-[1-(2,4-dichlorophenyl)-2-(1H- imidazol-1-yl)ethoxy-methyl]benzo[b]thiophene (sertaconazole, FI-7045, CAS 99592-32-2) versus miconazole has been studied in vitro against yeast-like fungi, dermatophytes and other filamentous fungi. Candida albicans was very sensitive to sertaconazole both in serotype A and serotype B strains (MIC = 0.21 micrograms/ml). Sensitivity of Candida non albicans species (MIC = 0.17 microgram/ml), Torulopsis (MIC = 0.09 microgram/ml) and Trichosporon (MIC = 0.09 microgram/ml) was also remarkable. For dermatophytes, partial inhibitions were observed at concentrations of 0.04 and 0.09 microgram/ml, the 50% inhibition ranging between 0.36 and 12.56 micrograms/ml for most strains. Filamentous opportunistic fungi were less sensitive to azoles, although sertaconazole MICs were lower than those of miconazole. Sertaconazole also proved to possess a remarkable fungicidal activity on all strains of Candida albicans under study.