Abstract Recombinant cDNAs encoding the α-subunits of G i1, G i2, G i3, G O and G S were transfected into COS cells with the pCD-PS mammalian expression vector. Expression of each G α was verified using subtype-specific peptide antisera on immunoblots. Quantitative immunoblotting of α and β subunits indicated: i) that there was no change in expression of endogenous β subunits, and ii) overexpression of α subunits could achieve a ratio of α:β > 25:1. Despite the excess of α over β, the G α subunits were found predominantly in the membrane fraction. The results demonstrate that G α subunits can attach to the membrane independently of βγ subunits.