The development of the adrenergic and cholinergic innervation of the ureter was studied by specific neurohistochemical methods. At birth, the musculature is devoid of adrenergic nerves. The first adrenergic nerve terminals start to appear 3--4 days after birth. During the following 4--6 weeks, the density of the nervous net-work increases rapidly to reach the final adult pattern of innervation. Cholinergic nerves were observed already before birth and their density increased rapidly during the first postnatal month. The development of a functional adrenergic neurotransmission appears later than the cholinergic innervation. Cholinergic nerves are thought to be possible sensory receptors. The development of the autonomic innervation appears to be related to the underlying maturation of the smooth musculature.