The sequential activation of the cyclin-dependent kinases by their partner cyclins underlies the progression of the cell cycle from quiescence through growth to cell division. More recently a role for these proteins and their inhibitors has been appreciated in several diverse renal and non-renal cell processes, including proliferation, development, differentiation, hypertrophy and apoptosis. The glomerulus represents a unique micro-environment in which to study the cellular outcome following injury, as each of the three resident cell types undergoes a specific and distinct response to a given stimulus. The mesangial cell is capable of marked proliferation, often accompanied by the deposition of extracellular matrix. In contrast, the podocyte has previously been considered a relatively inert cell, and the reparative proliferation of glomerular endothelial cells following injury has recently been described. There is currently increasing awareness of the need to prevent, control and ameliorate the progression of renal diseases. Knowledge of the cell cycle and an understanding of how this may be beneficially manipulated may be crucial to improving the outlook for patients with both diabetic and non-diabetic glomerular disease.