A precise description of the involvement of G proteins in regulation of the cardiovascular system is not possible at the present time although it is clear that they do have important regulatory roles. The cardiovascular system is composed of a variety of cell types, which are subject to control by several different hormones, as well as by hormones that have several different effects in the same cell type. Although, historically, variations in the type and number of receptors located on each cell have been used to explain this diversity of hormonal responses, we must now consider the large number and diversity of G proteins in any effort to understand the coordinated hormonal regulation of cellular functions. Given that there are eight known G proteins and several others have been speculated, each of which is composed of three subunits, each of which has several different forms, the possible combinations of subunits into functionally distinct G proteins is enormous. To place this newly described family of G proteins into the appropriate hormone signaling pathways will require a continued research effort. However, with recent progress in producing specific antibodies to each of the G protein subunits, it may now be possible to determine the specific receptor-effector functions of each G protein and their individual subunits.