The aim of this study was to investigate the effects of troglitazone (TRO)--a new insulin-sensitizing agent--on some metabolic parameters in an experimental model of hypertriglyceridemia and insulin resistance, hereditary hypertriglyceridemic rats, and to compare its effects with those of vitamin E, an antioxidant agent. Three groups of the above rats were fed diets with a high content of sucrose (70% of energy as sucrose) for four weeks. The first group was supplemented with TRO (120 mg/kg diet), the second one with vitamin E (500 mg/kg diet), and the third group served as the control. Vitamin E supplementation did not lower serum triglycerides (2.42 +/- 0.41 vs. 3.39 +/- 0.37 mmol/l, N.S.) while TRO did (1.87 +/- 0.24 vs. 3.39 +/- 0.37 mmol/l, p < 0.01). Neither TRO nor vitamin E influenced the serum levels of free fatty acids (FFA). Both drugs influenced the spectrum of fatty acids in serum phospholipids--TRO increased the levels of polyunsaturated fatty acids (PUFA) n-6 (36.04 +/- 1.61 vs. 19.65 +/- 1.56 mol %, p < 0.001), vitamin E increased the levels of PUFA n-3 (13.3 +/- 0.87 vs. 6.79 +/- 0.87 mol %, p < 0.001) and decreased the levels of saturated fatty acids (32.97 +/- 0.58 vs. 51.45 +/- 4.01 mol %, p < 0.01). In conclusion, TRO lowered the level of serum triglycerides but vitamin E did not have this effect in hypertriglyceridemic rats. Compared with TRO, vitamin E had a different effect on the spectrum of fatty acids in serum phospholipids.