PROGRESSION of proteins through the secretory pathway of eukaryotic cells involves a continuous rearrangement of macromolecular structures made up of proteins and phospholipids. The protein SEC14p is essential for transport of proteins from the yeast Golgi complex¹. Independent characterization of the SEC14 gene² and the PIT1 gene³, which encodes a phosphatidy-linositol/phosphatidylcholine transfer protein in yeast, indicated that these two genes are identical. Phospholipid transfer proteins are a class of cytosolic proteins that are ubiquitous among eukaryotic cells and are distinguished by their ability to catalyse the exchange of phospholipids between membranesin vitro⁴. We show here that the SEC14 and PIT1 genes are indeed identical and that the growth phenotype of a sec 14-1^ts mutant extends to the inability of its transfer protein to effect phospholipid transfer in vitro^4,5. These results therefore establish for the first time an in vivo function for a phospholipid transfer protein, namely a role in the compartment-specific stimulation of protein secretion.