Cell cycle proteins are critical regulators of proliferation in dividing cells. Paradoxically, accumulating evidence supports the view that core components of the cell cycle also play key roles in the development of terminally differentiated postmitotic neurons. Distinct cell cycle proteins including cell cycle-dependent kinases may contribute to naturally occurring programmed neuronal cell death in the developing mammalian brain. In addition, recent studies have uncovered a novel role for the cell cycle-associated ubiquitination machinery in the control of axonal growth and patterning in the developing brain. The underlying molecular mechanisms regulating these distinct cell cycle-based developmental events in neurons are just beginning to be understood.