Suisynchron treatment was applied to platform-kept gilts over 20 days. The dosage was 100 mg per animal and die. This was followed by 1,000 I.U. PMS and 250 I.U. HCG. Artificial insemination was applied five days after the first hormone administration and followed by one Gravigonan injection after another twelve to 15 days. Blood samples were drawn from those animals as well as from 20 gilts synchronised in the above way and another 20 untreated gilts from a production unit during the various phases of treatment and cycle. Those samples were used for assessment of cholesterol, lipoid-P, free fatty acids, triglyceride, and beta-lipoproteids. The levels of free and total cholesterol went up along with Suisynchron feeding, whereas lipoid-P and beta-lipoproteids declined. Free fatty acid levels went down with significance (P less than 0.01), and triglycerides increased (P less than 0.05). Cholesterol levels were not altered by PMS/HCG administration. The levels of lipoid-P, free fatty acids, and beta-lipoproteids rose to their magnitudes prior to Suisynchron treatment. Tirglycerides rose by 50 per cent. At the time of full oestrus triglyceride levels doubled (P less than 0.01). Unimportant rises were recorded also for cholesterol, beta-lipoproteids, free fatty acids, and lipoid-P. In animals with spontaneous oestrus all lipid parameters were ligher than in sows with full oestrus after synchronisation.