Developing neuronal networks in different brain structures, such as spinal cord, retina or cortex, reveal distinct patterns of spontaneous electrical activity. Synchronized bursts are either localized in discrete networks or propagate as waves of activity over large territories. In the cerebral cortex of newborn rodents and preterm human infants, spontaneous and evoked synchronized activity patterns can be observed even before the cortex has reached its six-layered architecture. The author will give an overview on spontaneous and stimulus-evoked neuronal activity patterns in the developing rodent and human cerebral cortex, will compare the experimental data obtained in different in vitro and in vivo models and will provide a hypothesis on the role of early electrical activity patterns for the formation of immature neuronal networks and for the control of programmed cell death.