Phosphatidylinositol/phosphatidylcholine transfer pro¬teins are characterized by their common feature, the ability to transfer phospholipids between membrane bilayers in vitro. In the cell, they fulfil specific roles at the interface between lipid metabolism and important cell functions that go beyond the in vitro observed phospholipid transfer activities. Experimental evidence indicates that the proteins are involved in complex regulations of lipid metabolism, which form an appropriate environment for essential transport processes. The focus of this review is the yeast PI/PC transfer protein Sec14p and its functional and sequence homologues in higher eukaryotes.