In a subarachnoid hemorrhage (SAH) model of the rat, there is a decreased tyrosine hydroxylase-like immunoreactivity in the adrenergic nerves around cerebral arteries. No altered reactivity is found in the superior cervical ganglion or in the nerve bundles around the internal carotid artery of cervical portion. The results suggest that SAH impares the initial step of catecholamine synthesis in the adrenergic nerves within the subarachnoid space.