We have raised a panel of monoclonal antibodies to PtdIns4P 5-kinase C purified from bovine brain [Divecha, Brooksbank and Irvine (1992) Biochem. J. 288, 637-642]. This panel includes antibodies which specifically recognize PtdIns4P 5-kinase C both in a native catalytically active condition, and/or when presented on Western blots. Some of the former antibodies will also inhibit PtdIns4P 5-kinase C activity. We have used the blotting antibodies to study the bovine tissue distribution of PtdIns4P 5-kinase C and its distribution in mammalian species. We have also studied its localization in Jurkat cells and found it to be predominantly bound to membranes, with only a minority localized to the cytoskeleton. Neither PtdIns4P 5-kinase activity nor PtdIns4P 5-kinase C, as detected by Western blotting, were increased in the cytoskeleton after stimulation of Jurkat cells with OKT3. These antibodies should prove to be extremely useful tools with which to study the regulation of PtdIns4P 5-kinase C.