Itraconazole is a broad-spectrum potent triazole antifungal agent. Its efficacy in treatment cannot always be explained by body fluid drug levels. In this study, itraconazole was shown to accumulate into host cells. Its intracellular accumulation in cells is greater than that of the antibacterial agent clindamycin, which is known for intracellular localization, and the uptake process does not appear to be active. This ability to reach high concentrations intracellularly may be an important property for the in vivo efficacy of itraconazole.