There are only few data on skeletal muscle lipid metabolism in diabetes. The aim of the present study was to examine effect of streptozotocin diabetes on incorporation of the blood-borne 14C-palmitic acid into different fractions of skeletal muscle lipids at rest and during contractile activity. The experiments were carried out on male Wistar rats. Streptozotocin was administered intravenously. The control rats received saline. Seven days later, the rats were anaesthetized and the calf muscles of one hindleg were made to contract for 1 min by stimulation of the sciatic nerve with tetanic pulses (30 tetani/min). Thereafter, 14C-palmitic acid was administered intravenously and the stimulation was continued for 5 min. The contralateral resting leg served as a control. Samples of the soleus, red and white gastrocnemius were taken. Lipids were extracted with chloroform/methanol and separated into the following fractions by means of thin layer chromatography: phospholipids, mono-, di-, and triacylglycerols, free fatty acids, cholesterol and cholesterol esters. Radioactivity of each fraction was counted. It has been found, that the label was always incorporated mostly into the fraction of triacylglycerols and phospholipids. Diabetes increased radioactivity of each lipid fraction, both at rest and during contractile activity, comparing to the respective values in the control rats. It is concluded that transport of the blood-borne free fatty acids into the myocytes and their incorporation into different lipid fraction increases in acute diabetes.