A rapid and simple method for determination of cefaclor in human plasma samples, by highperformance liquid chromatography (HPLC), was developed. This method includes a deproteinization with perchloric acid as extraction procedure. Plasma extracts were analyzed on a reversed phase column eluted with a mixture of acetonitrile and 0.01 M sodium dihydrogen phosphate solution, adjusted to pH 6.5 with potassium hydroxide (7:93, v/v), and detected by absorbance at 260 nm. Retention times for cefaclor and the internal standard were 5.2 and 7.2 min, respectively. The method was linear in the range of 0.5-30 Ill/ml and the detection limit of the method was 100ng/ml. This method was useful and suitable for determination of cefaclor after oral administration in healthy volunteers, and could be used for bioavailability and bioequivalence studies of the drug.