Studies have been conducted on the uptake and metabolism of unesterified fatty acid, free glycerol and 1-hexadecyl glyceryl ether by rat cardiac myocytes, and of fatty acid, intact triglyceride and the glyceryl ether by perfused rat hearts. Cardiac myocytes efficiently extracted, oxidized and esterified oleic acid, but demonstrated little ability to utilize free glycerol. Although the glyceryl ether was efficiently extracted by myocytes, it was neither hydrolyzed or esterified. The perfused heart also extracted and metabolized unesterified fatty acid, and the fatty acid released during lipolysis of circulating lipoprotein triglyceride. The glyceride glycerol, however, was largely recovered (90%) in the perfusate suggesting inefficient myocardial utilization of either free glycerol or partial glycerides. Myocardial extraction of glyceryl monoether was demonstrated, but the monoglyceride analogue was also unmetabolized by intact heart tissue. The results suggest that if monoglycerides are produced by the action of lipoprotein lipase on circulating triglycerides, reutilization of intact monoglycerides for higher glyceride synthesis is not a major fate of these products.