An improved HPLC method for the analysis of 7-ethoxycoumarin and its metabolites in liver-slice incubation media is presented. The assay is based on short-column gradient elution which permits baseline resolution of the parent drug and three metabolites with a fourfold reduction in analysis time relative to existing HPLC methods. Total assay run time is 10 min. Data establishing method performance are presented which show intra- and interassay precision and accuracy to be within 13 and 7%, respectively, for separately prepared quality control samples.