Long-chain acyl-CoA esters were extracted from freeze-clamped livers of fed and fasted rats according to the method of Mancha et al. [M. Mancha, G. B. Stokes, and P. K. Stumpf (1975)Anal. Biochem.68, 600–608] and analyzed on a radially compressed C₁₈, 5 μm, reverse-phase column using a gradient system consisting of acetonitrile and 25 mm KH₂PO₄, pH 5.3, at 254 nm. Total analysis time was 25 min. Eight peaks in the extract with carbon chain lengths of 12 to 18, which subsequently disappeared on alkaline hydrolysis, were identified. The major acyl-CoA peaks in the extract in order of increasing retention times were 14:0, 16:1, 18:2, 16:0, 18:1, and 18:0. Total liver long-chain acyl-CoA esters were 108 ± 11 and 248 ± 19 nmol/g protein for fed and fasted rats, respectively. On fasting (48 h) the levels of 18:2, 16:0, and 18:1 increased two-to threefold and that of 18:0 sixfold. The advantages of this method are that it not only provides a more direct determination of total tissue long-chain acyl-CoA esters, in that no decomposition of the CoA ester is involved, but it also detects the constituent molecular species.