Itraconazole is a recently developed triazole antifungal agent that inhibits cell membrane sterol biosynthesis. Itraconazole, in a dose-dependent manner, enhanced intracellular accumulation of daunorubicin and reversed the drug resistance in murine leukemia P388/ADR cells. In addition, itraconazole corrected the altered plasma membrane potentials of P388/ADR cells. The concentrations of itraconazole that reversed drug resistance are comparable to the plasma levels achieved by therapeutic dosage used in the treatment of fungal infections. Therefore, itraconazole is a potential candidate for in vivo use to reverse multidrug resistance in cancer with added benefit of its antifungal property. (J. Clin.