A chromatographic technique for determining tri-o-cresyl-phosphate (78308) (TOCP) and its putative metabolites was developed. Two milliliter (ml) samples containing TOCP and its possible metabolites o-cresyl-dihydrogenphosphate, di-o-cresyl-hydrogenphosphate, o- hydroxybenzyl-alcohol (90017), salicylic-acid (69727), o-cresol (95487), salicylaldehyde (90028), saligenin-cyclic-o-tolyl-phosphate (1222873), hydroxymethyl-tri-o-cresylphosphate, and dihydroxymethyl- tri-o-cresyl-phosphate were injected into a high performance liquid chromatographic system consisting of a reverse phase C18 cartridge fitted into an RCM-100 radial compression separation system, a guard column packed with C18 bondapack, an ultraviolet detector set at 240 nanometers, and an automated data processing system. The mobile phase consisted of a linear gradient of 25 to 80% acetonitrile in 2% aqueous acetic-acid. Analyte calibration plots indicated that the relationship between detector response (peak area) and injected amount was linear over a 100 fold concentration range. The detection limits were 50ng or less for TOCP and the other compounds. In recovery experiments, plasma, liver, and kidney samples obtained from cats were spiked with TOCP and the other compounds. The plasma samples were extracted with ether and the kidney and liver samples with acetonitrile. The extracts were cleaned up with hexane, dried over anhydrous magnesium-sulfate, and concentrated to 200 microliters. The concentrated extracts were analyzed by the procedure. Recovery of the spikes from the plasma, kidney, and liver ranged from 80.8 to 100.0, 35.1 to 100.0, and 30.8 to 98.7%, respectively. Recovery of highly polar acid metabolites such as salicylic-acid from the plasma was greater than from the liver or kidney. The authors conclude that the method is relatively fast and sensitive, and can quantitatively determine TOCP and nine of its putative metabolites in a single chromatographic step.