Striatal neurons exhibiting tyrosine hydroxylase-like immunoreactivity (TH-LI) were found in the adult rat. Most of these neurons had a cell body with a 10-20 microns diameter and several spiny dendrites. The number of striatal neurons with TH-LI was increased on the side ipsilateral to an electrothermic or 6-hydroxydopamine-induced lesion which had been placed in the regions around the substantia nigra.