The [14C]GABA uptake by slices (0.3 mm thick) of Wistar rat brain cortex was studied for its dependence on the GABA concentration in the medium, time of incubation and the presence of Ca2+. This process is characterized by the absence of saturation; the uptake by slices increases sharply when the concentration of exogenous [14C]GABA reaches 200 microM. Bicucullin (10(-4) M), an antagonist of GABA, inhibits the accumulation of GABA in the concentration of 0.2 microM by 60%, that evidences for a considerable contribution of the receptor binding to this process. The [14C]GABA uptake when Ca2+ is absent in the incubation medium and when its concentration is 10(-3) M is practically the same and comparatively low concentrations of Ca2+ (10(-6)-10(-4] decrease the GABA uptake.