Energy coupling for uptake of glycine and alanine in glycerol grown cells of Escherichia coli differs from that of the aromatic amino acids. Respiration and uptake of glycine and alanine show similar inactivations in cells exposed to high intensity violet light or to various concentrations of cyanide. In contrast, uptake of phenylalanine, tyrosine, and tryptophan is resistant to effects of light or cyanide. Anoxia largely inhibits uptake of glycine and alanine while that of the aromatic amino acids is only partially affected. Furthermore, ferricyanide (but not ferrocyanide) completely restores active uptake of aromatic amino acids under anoxic conditions but is without effect on glycine and alanine uptake. Adenosine 5′-triphosphate (ATP) concentration does not increase in anoxic cells exposed to ferricyanide, indicating that ATP cannot be responsible for this restoration. The data suggest that glycine and alanine represent amino acids whose transport shows a complete dependence on energy derived from respiration, while the energy for transport of the aromatic amino acids may be obtained from other sources.