1. Plasma lipids and lipoproteins have been studied in control subjects and patients with various types of steatorrhoea.
2. Low plasma cholesterol levels were found in malabsorbers and were associated with decreased amounts of low-density lipoprotein (LDL) in males and high-density lipoprotein (HDL) in females.
3. Serum triglyceride levels were normal in males, but exceeded control values in some of the females, due to an increase in very-low-density lipoprotein.
4. LDL composition was abnormal in both male and female malabsorbers, with a decreased proportion of cholesterol ester and an increased proportion of triglyceride. There was also an increased proportion of triglyceride in HDL.
5. These findings show that malabsorption markedly influences not only the concentration but also the composition of plasma lipoproteins.