Aim: To investigate the carnitine status and the effect of carnitine supplemen tation on serum lipid profiles in children with hyperlipoproteinaemia, a clinica l open trial was conducted at Hacettepe University Ihsan Dogramaci Children’s H ospital, Section of Nutrition and Metabolism. Methods: Patients were given carni tine at a dose of 100 mg/kg/d for 12 wk. Blood samples for the determination of lipid profile and carnitine levels and urine samples for carnitine levels were o btained on admission, at week 4 and week 12 of the study period. Results: A tota l of 41 children were enrolled in the study: 20 patients had type II heterozygot es, eight patients had type II homozygotes, three patients had type III, six pat ients had type V and four patients had secondary hyperlipidaemias. Serum and uri ne carnitine levels were within normal limits on admission. No significant corre lations were found between serum carnitine levels and serum lipid profiles. Seru m HDL and apolipoprotein A-I decreased significantly during the 12 wk of interv ention in type II heterozygotes. In type II ho mozygotes, total cholesterol and LDL levels at weeks 4 and 12 increased signif icantly compared to initial levels. No significant change was noted for lipid pa rameters in hyperlipoproteinaemia type V. Conclusion: The results of this trial demonstrated that carnitine supplementation was of no benefit for children with hyperlipidaemias, especially in primary hyperlipoproteinaemia type II heterozygo tes, homozygotes and typeV. Aim: To investigate the carnitine status and the effect of carnitine supplemen tation on serum lipid profiles in children with hyperlipoproteinaemia, a clinica l open trial was conducted at Hacettepe University Ihsan Dogramaci Children’s Hospital, Section of Nutrition and Metabolism. Methods: Patients were given carni tine at a dose of 100 mg / kg / d for 12 weeks. Blood samples for the determination of lipid profile and carnitine levels and urine samples for carnitine levels were o btained on admission, at week 4 and week 12 of the study period. Results: A tota l of 41 children were enrolled in the study: 20 patients had type II heterozygot es, eight patients had type II homozygotes, three patients had type III, six patients had type V and four patients had secondary hyperlipidaemias. Serum and uri ne carnitine levels were within normal limits on admission. No significant correlations were found between serum carnitine levels and serum lipid profiles. Seru m HDL and apolipoprotein AI dec reased significantly during the 12 wk of interv ention in type II heterozygotes. In type II ho mozygotes, total cholesterol and LDL levels at weeks 4 and 12 increased signif icantly compared to initial levels. No significant change was noted for lipid pa rameters in hyperlipoproteinaemia type V. Conclusion: The results of this trial demonstrated that carnitine supplementation was of no benefit for children with hyperlipidaemias, especially in primary hyperlipoproteinaemia type II heterozygo tes, homozygotes and type V.