A simple and sensitive high-performance liquid chromatographic method has been developed for determination of chlorogenic acid in rat plasma. Chlorogenic acid was extracted from plasma samples with methanol. HPLC analysis of the extracts was performed on a C18 column (250 mm × 4.6 mm i.d.5 µm particles). The mobile phase was acetonitrile -1% formic acid (9:91, v/v). The calibration plot was linear over the range 0.0420-2.10 µg mL-1 and the lower limit of quantification was 0.0420 μg mL-1. The method was reproducible and reliable with intra-day pre-cision better than 8.2%, inter-day precision better than 9.1 %, accuracy within ±8.3%, and mean extraction recovery above 84.4%. The validated method was successfully applied to pharmacokinetic studies of photogenic acid in rat plasma after administration of Luying decoction.