In our previous work it was found that in cystic fibrosis patients with and without pancreatic insufficiency, the fatty acid pattern of the plasma long chain, non-esterified fatty acid fraction is strikingly abnormal in comparison with the corresponding pattern of healthy subjects. However, other investigators have shown abnormal fatty acid patterns only in patients with pancreatic insufficiency. Therefore, we studied the plasma cholesterol ester fraction in cystic fibrosis patients of both types by gas liquid chromatography. It was found that the absolute total concentration of the plasma cholesterol esters in cystic fibrosis patients with and also without pancreatic insufficiency is significantly lower than in healthy subjects. Furthermore, the fatty acid pattern of this lipid fraction is significantly abnormal in both groups of patients, although to a lesser extent in patients without pancreatic insufficiency.