In order to determine if excess plasma glycerol originating in lipolysis increased the synthesis and secretion of lipoproteins in the liver of Zucker fa/fa rats, labelled (1–14C) glycerol was injected in vivo in the jugular vein, in the presence of (9,10–3H2) oleic acid and Triton WR 1339 to block plasma clearance of neoformed lipoproteins and to be secreted into the blood by the liver. Glycerol stimulated hepatic synthesis of lipids in the Zucker fa/fa rat. This resulted in an increased secretion by the liver of VLDL and lipoproteins comparable to chylomicr