Mammalian cells respond to external stimuli by activation of a variety of signal transduction pathways, which culminate in stereotypical responses, such as proliferation, growth arrest, hypertrophy, differentiation, or apoptosis. In vertebrates the actions of many stimuli resulting in proliferative or hypertrophic growth converge on a set of cellular kinase cascades, which are collectively called the mitogen-activated protein (MAP) kinase cascades. These MAP kinases have been implicated in vascular smooth muscle cell proliferation and hypertrophy, responses that are central to the pathophysiology of hypertension. In this review, we will examine how proliferative and hypertrophic stimuli activate these MAP kinase cascades, what are the consequences of that activation on gene expression, and how do these signals drive the cell into one of the stereotypical responses noted above.