Purpose. Immunohistochemical and autoradiographic evidence provides anatomical support for the role of taurine as an inhibitory neurotransmitter in amacrine cells (ACs) of some mammalian and amphibian retinas. However, the pharmacological actions of taurine on second order neurons is indistinguishable from glycine, suggesting that it may be an analog of glycine within glycinergic ACs. In this study we examined the extent of colocalization between the inhibitory neurotransmitters taurine, glycine, and GABA, using high-resolution immunohistochemistry. Methods. Mudpuppy retinas were fixed in 4% formaldehyde, 0.2% acrolein and 0.2% glutaraldehyde for 2 hrs, rinsed in buffer, dehydrated in acetone, infiltrated, and embedded in Unicryl (BioCell) acrylic resin. Consecutive O.Sum transverse sections were incubated overnight with antisera raised in rabbit against protein-glutaraldehyde conjugates of GABA (Chemicon, 1:200), glycine (Chemicon, 1:200), or taurine (BioDesign 1:100). Primary antisera was visualized with goat anti-rabbit 1 nm gold (BioCell, 1:100) intensified with silver (BioCell). Serial sections were aligned so that different immunoreactivities could be localized in the same cell profiles. Results. Of 150 ACs labeled by the three antisera, 65% were GABA-immunoreactive (-IR), 34% were glycine-IR, and 19% were taurine-IR. Virtually none of the glycine-IR ACs were taurine-IR, but 24% of the GABA-IR ACs were taurine-IR. Over 70% of the taurine-IR ACs were GABA-IR. Conclusions. These results support the existence of separate populations of glycinergic and taurinergic ACs in the mudpuppy retina. In addition, a subpopulation of GABAergic ACs contain taurine, and may release it as a co-transmitter. It remains to be determined if these cells release taurine svnaoticallv.