The development of the morphological features of neurons in the lateral geniculate nucleus of monkeys from the late foetus to the age of one month was studied in rapid Golgi preparations. Most of the neuronal types found in the adult are already recognizable at birth. They differ from their mature forms mainly in having dilatations along their dendrites (growth cones or buds), and a large number of spiny or hair-like processes on their dendrites and somata. During postnatal maturation, first the growth cones and buds regress. Then the number of spines and hairs increases, before decreasing again to reach adult values at around one month. All the main neuronal types follow a similar sequence of maturation, but neurons in magnocellular laminae mature before those in parvocellular. These maturational stages take place during a period of overall growth in cell body size and dendritic length, during which spatial resolution of the neurons is increasing, and when the animal is most susceptible to the effects of visual deprivation.