AbstractThe energy, ionic, and pH dependence of the influx of labelledL‐glutamic acid has been studied in frog sciatic nerve(1)The addition of 10−2MD‐glucose to the incubation medium was found to inhibit the total influx of glutamic acid from a 10−6M solution by about 40%.(2)The rate of influx was found to be sensitive to the temperature of the bathing medium. Influx was found to increase with temperature in a linear manner from 10°C to 34°C; above 34°C, the rate of influx dropped with increased temperature.(3)At room temperature, the effect of metabolic inhibitors on total influx ranged from 18% inhibition with aresenate to 62% with DNP. Increasing the incubation temperature to 34°C increased the percentage inhibition, a maximum inhibition of 86% occurring with DNP.(4)The cardiac glycoside ouabain (10−3M) slightly inhibited influx (15%).(5)Reduction of the sodium concentration to 2.3 mM resulted in an 82% decrease in total influx. Omission of potassium or a tenfold increase in potassium concentration had no significant effect on influx. Omission of calcium resulted in a slight stimulation of uptake (16%); a tenfold increase in calcium concentration was slightly inhibitory (15%).(6)No relation was found between influx and the pH of the incubation medium. Lowering the pH to 5.4 or raising it to 9.4 had no significant effect on influx.(7)It is concluded thatL‐glutamic acid influx in frog sciatic nerve is probably associated with an energy‐