Involved in the transfer of neutral lipids, including cholesteryl ester and triglyceride, among lipoprotein particles. Allows the net movement of cholesteryl ester from high density lipoproteins/HDL to triglyceride-rich very low density lipoproteins/VLDL, and the equimolar transport of triglyceride from VLDL to HDL (PubMed:24293641, PubMed:3281933, PubMed:3600759). Regulates the reverse cholesterol transport, by which excess cholesterol is removed from peripheral tissues and returned to the liver for elimination (PubMed:17237796). {ECO:0000269|PubMed:24293641, ECO:0000269|PubMed:3281933, ECO:0000303|PubMed:17237796, ECO:0000305|PubMed:3600759}. This is the function of Ensembl gene identifier ENSG00000087237 (CETP, cholesteryl ester transfer protein).