A technique for the simultaneous identification and quantitation of 13 hydroxycoumarin and indandione anticoagulant drugs and rodenticides from human serum by reversed-phase liquid chromatography with diode-array detection has been developed. High-performance liquid chromatography was performed using gradient elution with an acetonitrile and phosphate buffer on a Nucleosil ODS column. Ultraviolet spectra from 200 to 400 nm were recorded on-line during the analysis and compared with spectra stored in a library. For the spiked 2 mL of serum, acidic and alkaline liquid-liquid double extraction with diethylether-ether acetate (50:50, v/v) was conducted, and recoveries greater than 60% for most compounds were found. The detection limit was approximately 25 or 50 ng/mL for all components except for difethialone and fluindione, for which it was approximately 100 ng/mL. The standard calibration curves were linear from the detection limit to 5000 ng/mL. The within-run precision coefficient of variation (CV) was less than 10%, and the between-run precision CV was less than 20%.