The content of non-esterified fatty acids (NEFA) and their CoA and carnitine esters is low in normoxic cardiac tissue. The majority of fatty acids is esterified in the triacylglycerol and phosphoglyceride pool. During myocardial ischaemia beta-oxidation of fatty acids is inhibited. In addition, turnover of the esterified fatty acid pools is most likely disturbed. Accumulation of hydroxy fatty acids, acylCoA and acylcarnitine rapidly occurs after the onset of ischaemia. The accumulation of NEFA is a slower process. In addition to extracellular sources, NEFA originate also from intracellular lipid pools, most likely from phosphoglycerides. Although it has been suggested that activation of phospholipase A2 occurs in ischaemic tissue, the mechanism underlying the enhanced degradation of phosphoglycerides ist still incompletely understood.