The appearance and development of tyrosine-hydroxylase-immunoreactive cells were studied using whole mounts of postnatal rat retinas. The two classes of cells described in the adult retina were observed in the young rat. Small unipolar cells appeared as soon as the day of birth in the superior retina and large stellate cells by postnatal day (PND) 7. By PND 10, their number reached that of stellate cells of the adult-retina. It is hypothesized that small unipolar cells are transformed into large stellate cells as they mature. Several arguments are put forward to support this conclusion, the most important of which is the appearance of peripheral crescents containing a high density of small cells which disappear proportionately as the number of large stellate cells increases. The development of the vasculature was also studied. By PND 7, it was more developed in the temporal superior quadrant, in the region where the first stellate cells appeared.