Recent studies suggest that the antifungal agents itraconazole, bifonazole, and ketoconazole affect calcium-mediated signal transduction in Trichophyton rubrum. We have now examined the effects of azole-antifungal agents on cell membrane function in T. rubrum, by analysing the effects of itraconazole, bifonazole, ketoconazole, and lanoconazole on ionomycin-induced changes in intracellular calcium concentration ([Ca2+]i). Addition of 1 μm ionomycin to the culture medium produced a persistent increase in [Ca2+]i. While treatment with 1·5–15 nM of lanoconazole or bifonazole for 24 h did not affect this ionomycin-induced increase in [Ca2+]i, 30 nM of these agents resulted in a transient increase in [Ca2+]i rather than the usual sustained increase in [Ca2+]i. This transient ionomycin-induced increase in [Ca2+]i was also observed after treatment with only 1·5 and 3 nM of ketoconazole or itraconazole. Incubation in the presence of lanoconazole or bifonazole at [ges ]150 nM, and ketoconazole or itraconazole at [ges ]15 nM inhibited both the persistent and transient ionomycin-induced increase in [Ca2+]i. On the basis of these findings, it is suggested that azole antifungal agents disturb membrane function in T. rubrum, and that one manifestation of this effect is the disruption of the ionomycin-induced increase in [Ca2+]i. We report that the ionomycin-induced increase in [Ca2+]i is more sensitive to low concentrations of ketoconazole and itraconazole compared to bifonazole and lanoconazole.