AbstractA study of the transport of3H‐hypotaurine by rat retina has been carried out. The process is markedly sodium and temperature dependent. Kinetic analysis of the data revealed two values for the affinity constant (K) of 4.91 μM and 1,071.3 μM. Some related and unrelated amino acids were examined as competitive inhibitors of3H‐hypotaurine transport. Only GABA and β‐alanine exhibited appreciable inhibitory activity. Taurine, glycine, and guanidine ethane sulfonate were not inhibitors.3H‐hypotaurine uptake was similarly distributed in the retinal subcellular fractions P1and P2. The active uptake of3H‐Hypotaurine by retinas of the rat and other species including chick and frog was studied and compared to cerebral cortex slices. The chick retina was similar to the rat in its capacity to transport hypotaurine whereas frog exhibited fourfold less activity. Slices of cerebral cortex from rat and chick exhibited hypotaurine uptake but again the magnitude of the transport was three to fourfold less than in the compara