Serum lipids and lipoproteins were investigated in two girls who suffered from total lipodystrophy, in their family members, and in two brothers suffering from Cockayne syndrome. Hyperlipoproteinemia type IIb (Fredrickson) was detected in one case with total lipodystrophy. Very low levels of serum high density lipoprotein cholesterol (HDL-Ch) were observed in both of total lipodystrophic cases, in most of their first degree relatives, and in one of patients with Cockayne syndrome. Because total lipodystrophy and the Cockayne syndrome belong to ageing syndromes they can serve as a useful model of premature arteriosclerosis and the defect lipid metabolism.