The pattern of neurogenesis of the cat hypothalamus was studied by the use of the [3H]thymidine autoradiographic method. The neurons of the cat hypothalamus are nearly all generated in a period from embryonic days E21 to E35, and in most cases the neurons in a single nucleus are generated over a much shorter period. The dominant gradient along which the cells are organized is lateral-medial (outside-in). This gradient was apparent in all nuclei except the periventricular and arcuate nuclei. Two other gradients were observed in some, but not all, nuclei. These were along the dorsoventral and the posteroanterior axis. The dorsoventral gradient was uniformly less pronounced than the lateromedial gradient. The posteroanterior gradient was most obvious in the mammillary complex. An analysis of the data suggests that the neurons of individual nuclei do not necessarily have a unique production history. This suggests that insofar as nuclear formation is concerned, factors such as the parental population generating the neurons that populate a nucleus, as well as the early neuronal interconnections, may play a more important role than the birthdates themselves. © 1985.