A high-performance thin-layer chromatographic method was developed for the determination of ketoconazole. The sample was separated on a silica gel 60 F254 plate and developed in ethanol-acetone-1.0 mol l-1 H2SO4 by means of an automatic multiple-development system. The area of the spot was quantified by a TLC scanner at a wavelength of 298 nm. A linear calibration curve was established over the range of 3-20 μg/ml of ketoconazole, with a correlation coefficient of 0.9992. The relative standard deviations for intraday and interday precisions, for three replicate determinations, were found to be 1.72% and 0.69% for 5 μg/ml and 2.18% and 0.94% for 10 μg/ml of ketoconazole, respectively. The average percentage recoveries of ketoconazole shampoos (Nora, Kenalyn, and Nizoral) and ketoconazole creams (Nizoral, Fungasin, and Ketazon) were found to be 96.10, 97.06, and 99.58, and 96.77, 97.26, and 95.74, respectively. This method has been applied to the determination of ketoconazole in various pharmaceutical dosage forms. Common excipients in formulations do not interfere. This method is simple, precise, accurate, and inexpensive. It should be used for routine analysis.