Although the role of G protein-coupled receptors in the regulation of metabolic, secretory and contractile responses is well established, they have only recently been recognized as important mediators of cellular growth and differentiation. G protein-coupled signaling pathways had been previously thought to be totally independent of the tyrosine kinase receptor pathway. It was previously believed that molecular switches responsible for growth factor tyrosine kinase receptor signaling and G protein-coupled signaling were divided into a distinct sets of protein families. Recent evidence has demonstrated, however, that G protein-coupled receptors can crosstalk to tyrosine kinase signaling. In the past few years several groups have found that G protein-coupled receptors utilize non-receptor tyrosine kinases, mostly that of Src family, and some adapter proteins, to regulate tyrosine kinase cascades in cells.