The subcellular distribution of the enzymes which phosphorylate phosphatidylinositol sequentially to form phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate was investigated in rat liver. Whilst phosphatidylinositol kinase is present in golgi, lysosomes and plasma membranes, the kinase that forms phosphatidylinositol 4,5-bisphosphate is localized predominantly at the plasma membrane. The role of the inositol lipid kinases in cell function is discussed.