We have examined the temperature dependence of maximal flux, J M , the half-saturation value, K m , and of the linear components, k, of the initial transport flux for l-methionine, l-tryptopah, glycine, l-alanine, α-aminoisobutyric acid and l-phenylalanine in Ehrlich ascites cells. For l-alanine, α-aminoisobutyric acid and l-phenylalanine we examined the initial flux in transport and in exchange for cells in Na +-containing and in Na +-free media. The maximal flux in transport falls with decrease in temperature, the activation energies falling in the range 11–20 kcal/mole. The K m decreased with decrease in temperature for l-phenylalanine and l-tryptophan with apparent activation energies of 20 and 15 kcal/mole respectively, For l-methionine, glycine and l-alanine the K m showed no dependence on temperature whereas for α-aminoisobutyric acid in increased as the temperature fell. For all amino acids, the K m appeared to be more variable a parameter of the initial flux than was the maximal flux. The results for the linear component of the uptake, k, also were highly variable, but k did decrease with a fall in temperature with activation energies falling in the range 5.8–17.7 kcal/mole.