Heterotrimeric, guanine nucleotide binding proteins, known as G proteins, provide signaling mechanisms for the serpentine family of receptors. Recent studies indicate that the alpha- as well as the beta gamma-subunits of the G proteins are involved in the regulation of several cellular responses. Some of these responses proved to be critical for the regulation of cell growth and differentiation. Studies using the constitutively activated mutants of the G alpha subunits and the overexpression of G beta gamma subunits have indicated that these different subunits regulate cell proliferation through diverse signaling pathways involving distinct low molecular weight GTPases and specific protein kinases. The integrated networking between these different pathways finally defines the coordinated regulation of cell proliferation. This review briefly summarizes our present understanding of the different signaling mechanisms involved in the regulation of cell proliferation by the different G alpha and G beta gamma subunits.