Phosphoinositide-specific phospholipase C (PI-PLC) plays a pivotal role in regulation of intracellular signal transduction from various receptor molecules. More than 10 members of human PI-PLC isoforms have been identified and classified into three classes ␤, ␥, and ␦, which are regulated by distinct mechanisms. Here we report identification of a novel class of human PI-PLC, named PLC⑀, which is characterized by the presence of a Ras-associating domain at its C terminus and a CDC25-like domain at its N terminus. The Ras-associating domain of PLC⑀ specifically binds to the GTP-bound forms of Ha-Ras and Rap1A. The dissociation constant for HaRas is estimated to be approximately 40 nM, comparable with those of other Ras effectors. Co-expression of an activated Ha-Ras mutant with PLC⑀ induces its translocation from the cytosol to the plasma membrane. Upon stimulation with epidermal growth factor, similar translocation of ectopically expressed PLC⑀ is observed, which is inhibited by co-expression of dominant-negative Ha-Ras. Furthermore, using a liposome-based reconstitution assay, it is shown that the phosphatidylinositol 4,5-bisphosphate-hydrolyzing activity of PLC⑀ is stimulated in vitro by Ha-Ras in a GTP-dependent manner. These results indicate that Ras directly regulates phosphoinositide breakdown through membrane targeting of PLC⑀.