methylglutaryl, dodecanedioyl and hexadecanedioyl carnitines are described. The dicarboxylic acylcarnitines were prepared from eight equivalents of cyclic anhydride or isopropylidene ester of the dicarboxylic acid and carnitine chloride in trifluoroacetic acid solution. Long chain dicarboxylic acylcarnitines were additionally purified by partitioning between water and n-butanol. Stable isotope labeled