Abstract The degree of coupling ( q) and the efficacy of accumulation > − X A> /nu> A ch J A =0 i.e. the maximum static head accumulation ratio of α-aminoisobutyrate accounted for by ATP hydrolysis, have been assessed according to the rules of irreversible thermodynamics by comparing the mutual effect between α-aminoisobutyrate influx and ATP hydrolysis. Whereas the rate of α-aminoisobutyrate transport slightly rises with that of ATP hydrolysis, the latter was found to be completely independent of α-aminoisobutyrate transport. It was concluded that within the limits of experimental error, the degree of coupling and the efficacy of accumulation is negligible. In other words, there is no evidence that α-aminoisobutyrate transport in Ehrlich cell is directly energized by ATP hydrolysis.