This study was conducted to evaluate changes in plasma concentration and urinary excretion of carnitine, as well as plasma lipid level and fatty acid composition, caused by short term supplementation of carnitine in humans. Ten healthy male subjects (21.2 $pm$ 0.5 years old) received oral carnitine supplementation (4 g/day) as tablets for two weeks. Fasting blood and random urine samples were collected from each subject both prior to and at the end of carnitine supplemention program. Following the 2 weeks of carnitine supplementation, plasma total carnitine (TCNE) concentration increased 20% (85.1 $pm$ 7.4 vs 67.3 $pm$ 9.1 $mu$ mol/1, p> 0.05), while urinary excretion of total carnitine increased ten times compared to the value measured prior to the supplementation (3051 $pm$ 692 vs 278 $pm$ 90.1 $mu$ mol/g creatinine, p < 0.01). Non-esterified carnitine (NEC) comprised from 71 to 88% of TCNE in plasma, and from 32 to 40% of TCNE excreted in the urine. Two weeks of carnitine supplementation in healthy adults significantly elevated plasma level of acid soluble acylcarnitine (ASAC) which is esterified mostly with short chain fatty acids (21.6 $pm$ 1.6 $mu$ mol/l) compared to the value measured prior to the supplementation (6.4 $pm$ 0.8 $mu$ mol/l) (p < 0.05). Carnitine supplementation significantly increased plasma HDL-cholesterol level (p < 0.05), and decreased the atherogenic index (p < 0.05), but failed to cause any significant change in plasma levels of total cholesterol, triglyceride, and free fatty acids. Plasma triglyceride and phospholipid fatty acid compositions were not significaly affected as well by the oral supplementation of carnitine in subjects with normal range of blood lipid levels.