The Gα subunits of the G 12 family of heterotrimeric G proteins, Gα 12 and Gα 13 , are closely related in sequences and some effectors, but they often act through different pathways or bind to different proteins. We have examined subcellular distribution of these two G proteins and found that endogenous Gα 12 and Gα 13 localize in membrane and cytoplasmic fractions, respectively. Exogenously expressed Gα 12 and Gα 13 also localize in membrane and cytoplasmic fractions, respectively, in COS-7 cells. Stimulation of lysophosphatidic acid receptor coupled to Gα 13 markedly promotes the translocation of Gα 13 from cytoplasm to membrane. This different localization of Gα 12 and Gα 13 may explain some of the nonoverlapping actions of Gα 12 and Gα 13 .