Several authors recently reported that inhibition of protein synthesis by starvation for a required amino acid, by cycloheximide or by other inhibitors produces a rapid decay in specific transport activity of amino acids in Neurospora and animal tissues ( Adamson, Langellutig and Anast, 1966; Elsas and Rosenberg, 1967; Wiley and Matchett, 1967; Yamada, Clark and Swendseid, 1967). It was suggested in these papers, as one or as the sole interpretation of the results, that protein synthesis is an obligate requirement for the maintainance of carrier-proteins with short half-lives (i.e. rapid turnover). The results presented here indicate that, in a similar situation analysed in yeast, this interpretation has to be eliminated. They suggest that the inhibition of amino acid transport activity is due to a pool of endogenous amino acids which accumulate as a consequence of the inhibition of protein synthesis.