Carnitine (β -hydroxy-γ -trimethylaminobutyric acid) facilitates the transfer of activated long-chain fatty acids from the cytoplasm to the mitochondria, the site of their β -oxidation. Carnitine deficiency results in a reduced usage of fatty acids in energy production and therefore the appearance of clinical symptoms such asmyalgia and muscle weakness. In the present study, serum carnitine levels were measured in 45 children and 20 adults with homozygous beta thalassemia. A decrease in serum carnitine levels (total, free and acyl) was found, without any evidence of disorder in the process of mitochondrial β -oxidation. The possible cause of this finding could be related to a reduced hepatic carnitine biosynthesis. Conclusion: In patients with homozygous beta thalassemia, the reduction of serum carnitine levels might play an important role in the appearance of muscular dysfunction. It is possible that l -carnitine administration in these patients might improve or even resolve the aforementioned symptom. Carnitine (β -hydroxy-γ -trimethylaminobutyric acid) facilitates the transfer of activated long-chain fatty acids from the cytoplasm to the mitochondria, the site of their β -oxidation. Carnitine deficiency results in a reduced usage of fatty acids in energy production and therefore the appearance of clinical symptoms such as musculargia and muscle weakness. In the present study, serum carnitine levels were measured in 45 children and 20 adults with homozygous beta thalassemia. A decrease in serum carnitine levels (total, free and acyl) was found, without any evidence of disorder in the process of mitochondrial β -oxidation. The possible cause of this finding could be related to a reduced hepatic carnitine biosynthesis. Conclusion: In patients with homozygous beta thalassemia, the reduction of serum carnitine levels might play an important role in the appearance of muscular dysfunction. It is possible that l-carnitine administration in these patients might improve or even resolve the a forementioned symptom.