In a small series (n = 4) of young, lean males, the daily addition for 2 weeks of 200 g sucrose to the diet, caused no marked changes in the mean values of serum triglycerides, basal plasma insulin, Intralipid® fractional turnover rate or adipose tissue lipoprotein lipase activity. In agreement with our earlier experience, the fatty acid composition of lipoprotein phosphoglycerides, particularly high-density lipoprotein (HDL) phosphoglycerides, appear to be a sensitive indicator of hormonal and dietary influences on the serum lipid and lipoprotein metabolism. Thus, after sucrose ingestion, there was a significant decrease in linoleic acid (18:2) content and a tendency for a reduction in palmitic acid (16:0) in HDL phosphoglycerides. It is suggested that these changes in fatty acid composition of the phosphoglyceride moiety might be an expression for a depression of the major lecithin synthesis pathway, the cytidin-diphosphate (CDP)-choline diglyceride pathway in the liver. Furthermore, changes in the fatty acid composition of HDL lecithin, the specific substrate in the lecithin:cholesterol acyl transferase reaction, might be of relevance in the metabolism (particularly in the removal) of serum triglyceride-carrying lipoproteins