This study was carried out to investigate the morphology, distribution and co-localization of calbindin D-28k and parvalbumin-containing GABAergic cells in the midbrain of the cat. The results obtain by immunocytochemical observation were as follows : 1. Calcium binding protein calbindin D-28k and parvalbumin immunoreactive neurons were mainly found in the red nucleus, substantia nigra, oculomotor nucleus and locus ceruleus of the cat midbrain. 2. Parvalbumin immunoreactive cells in the red nucleus were more than twice in number compared to the calbindin D-28k immunoreactive cells. 3. Calbindin immunoreactive cells in the substans nigr were more than twice in number compared to the parvalbumin immunoreactive cells. 4. Double labelled immunocytochemical study revealed that parvalbumin and GABA were colocalized neurons in the same cells of the transverse section of the midbrain. 5. Calbindin D-28k and parvalbumin-immunoreactive cells were round, oval, spindle or polygonal in shape and were 15~20 micrometer in diameter. Positive neurons displayed unipolar, bipolar, or multipolar feature.