The aim of this text is to integrate the processes of protein phosphorylation and dephosphorylation into the complex pathways by which cellular proliferation is driven, bringing together the many different systems of control implicated in the regulation of cell growth. Presents a survey of protein phosphorylation roles in the control of cellular proliferation and differentiation. A large number of protein kinases and phosphatases have been characterised in higher cells, and have been shown to be involved in signal transduction pathways by which growth factors, mitogens, and extracellular agents exert proliferative effects on cells. Important subjects covered include control of gene expression at the transcriptional and translational levels, and roles of the cdk kinases and cyclins in cell cycles regulation. Describes all major families of protein kinases of significance to growth regulation.