GABA and choline accumulation has been investigated in 8-day cultures of 10-day chick embryo neuroretinal cells. Accumulation of ( 3H)-labelled GABA or choline (1 μ m) was linear for about 5 min under most conditions. Kinetic analysis suggested that high affinity uptake systems exist for both GABA and choline, with apparent K m values of 0·5–1·0 μ m for GABA and 0·2–0·4 μ m for choline. Accumulation of GABA was strongly temperature-sensitive and sodium-dependent, and was largely eliminated by 50 μ m-nipecotic acid, though not by the GABA analogues β-alanine or l-2,4-diaminobutyric acid at concentrations up to 5 m m. Choline accumulation was also temperature-sensitive, but was only about 40% inhibited by sodium-free medium or by 20 μ m-hemicholinium III. Comparison of standard cultures (both neurones and glia present) with both glial-enriched cultures and neurone-enriched cultures revealed the following contrasts. GABA accumulation was much greater in neurone-enriehed than in standard cultures, and was very low in glial-enriched cultures. Choline accumulation, however, was lower in neurone-enriched than in standard cultures, and in glial-enriched cultures reached higher levels than did GABA uptake. These results suggest a predominantly neuronal uptake system for GABA, while choline accumulation seems less specific and may include a large glial component (some choline perhaps being used for membrane biosynthesis). These interpretations were confirmed by autoradiographic studies. ( 3H)-GABA labelled many (but not all) neuronal cell bodies and processes in standard and especially in neurone-enriched cultures. A few glial cells were also labelled in standard cultures, and all labelling was abolished by Na +-free medium. ( 3H)-Choline, by contrast, labelled only a small proportion of neuronal cells prominently, and most silver grains were widely distributed over the background of glial cells.