Abstract Stereotaxic lesions were discretely placed in the substantia nigra in five cats. Fiber degeneration was studied using the Nauta-Gygax technique. The findings suggest that the greatest efferent outflow of the substantia nigra is to the ipsilateral midbrain tegmentum and tectum. Other degenerating fibers and preterminal branchings were seen in the ipsilateral nucleus ruber, subthalamic nucleus, inferior colliculus, nucleus of Darkschewitsch, nucleus ventralis anterior thalami and nucleus ventralis medialis thalami. No preterminal degeneration could be seen in the globus pallidus, putamen or caudate; a few degenerating fibers were seen coursing through each of these nuclei.