It has long been recognized that the balance between cellular proliferation and cell death during embryogenesis is a key factor in formation of the CNS. The recent definition of molecular mechanisms that drive the cell-division cycle and programmed cell death provides an opportunity to investigate the molecular interactions that co-ordinate cell-cycle regulation with CNS-pattern formation, neural differentiation and histogenesis. It is proposed that not only is the cell-division cycle regulated by developmentally controlled molecular signals to halt or proceed, but gene products that drive the cycle can also influence the course of neural differentiation and apoptosis.