Homotypically pure cultures of rat brain astrocytes were used to examine some aspects of non-neuronal A-system (alanine preferring) amino acid uptake. The A-system specific probe, alpha-aminoisobutyric acid is transported rapidly, and a steady state distribution ratio of 9-25 is reached after 30 minute incubations. Kinetic estimates derived from uptake progress curves indicated a Km of 1.35 mM and a Vmax of 133 nmol/min/mg protein. Uptake is reduced in the absence of either Na+ or K+. Elevations in extracellular K+, a putative metabolic modulator of neuroglia, did not affect uptake.