Carnitine is responsible for several chemical processes. including lipid metabolism, nerve cell conduction, reduction in muscle hypotonia, and limitation in oxidative damage to cells. In patients with Down syndrome (DS), the process of growth is behind that of normal children and neuromuscular control is attained somewhat later. The purpose of this study was to assess variation in levels of carnitine in normal and DS children and the relationship between the amount of carnitine and age. The study involved 30 (15 girls, 15 boys) normal children and 40 (20 girls, 20 boys) DS patients of Turkish ancestry, 6 months to 13 years of age. Carnitine level was determined using Deufel's enzymatic method. Carnitine level was significantly lower in DS patients compared with normal children between 6 months to 5 years of age. Between 5 and 13 years of age, the level of carnitine was about the same in both the normal and DS groups. The results suggest that carnitine level shows a different pattern of age related increase in DS compared to normal children. Published 2001 Wiley-Liss, Inc.