During the past year, there has been significant progress in the knowledge of mechanisms involved in the intracellular transduction of extracellular signals. These advances have allowed a more detailed understanding of how receptors involved in contraction and relaxation of smooth muscle cells couple to intracellular effector systems and of the growth response that characterizes the behavior of blood vessels in hypertension. A large measure of this progress relates to identifying receptor subtypes of regulatory proteins that modulate activation of intracellular or membrane enzymes participating in contraction, relaxation, and growth as well as new pathways of signal transduction. Major new findings in mechanisms of cell signaling and growth in vascular smooth muscle are discussed in part I, and their involvement in hypertension are discussed in part II.