Neurons and axons were characterized by means of an antiserum against LH-RH in hypothalamus of human faetuses from the 13th week of gestation until birth. The morphology and the elective localization of neurons and axons in the mediobasal hypothalamus, premamillary area and in lamina terminalis, and the termination of axons, particularly those of the tubero-infundibular tract, are described. The results obtained permit discussion of hypothalamic control of gondotropic secretion in the human faetus from the 13th week.