A method for determining tissue levels of Coenzyme A and various short-chain-length acyl-CoA derivatives using high-performance liquid chromatography is presented. Separation of the various compounds was accomplished using a reverse-phase Spherisorb ODS II, 5-μm C₁₈ column. Mobile-phase solvents were (a) potassium phosphate, 220 mm; thiodiglycol (2,2-thiodiethanol), 0.05% (v v ), pH 4.0 and (b) methanol, 98%; chloroform; 2% (v v ). The various acyl-CoA derivatives were detected by monitoring the column effluent at 254 nm. Nearly baseline separation was obtained for a standard mixture of free CoASH, methylmalonyl-CoA, β-hydroxy-β-methylglutaryl-CoA, succinyl-CoA, acetoacetyl-CoA, acetyl-CoA, propionyl-CoA, isobutyryl-CoA, β-methylcrotonyl-CoA, and isovaleryl-CoA. CoA derivative profiles were determined in neutralized perchloric acid extracts of perfused rat hearts and livers and of isolated rat liver mitochondria to demonstrate the utility of this method for assessing the levels of CoA derivatives in biological samples.