The skeletal muscle and the myocardium (musculature) are involved in the turnover rate of free fatty acids (FFA) with a third. Disturbances of the FFA metabolism of the musculature result in a restriction of the function which appears as a diminished contractility and, as far as the myocardium is concerned, additionally as arrhythmias. Moreover the restriction of the FFA utilization by the muscles plays a role in the origin of hyperlipacidaemias participating in the pathogenesis of various acute and chronic extramuscular functional disturbances (e.g. thrombophilia, disorders of the capillary circulation, hyperlipoproteinaemia, postnatal hypoglycaemia). With regard to its clinical relevance a survey is given of the FFA muscular metabolism. The author deals with the factors affecting the FFA netto bilance of the muscles and in this connection the regulation of the lipolysis, the triglyceride synthesis and the fatty acid oxidation. Finally the relation between the FFA and glucose metabolism in the muscles is described.