A wealth of structural information on amino acid transport-related proteins has appeared during the last 4 years. Up to date, these proteins are structurally classified into five different families: cationic amino acid transporters; superfamily of sodium- and chloride-dependent transporters; family of gluta-mate transporters, which includes structurally related zwitter-ionic amino acid transporters; family of sodium symporters for sugars, amino acids, vitamins and nucleosides; and a family of possible specific activators or subunits of amino acid transporters. The present review deals with the structural classification of different amino acid transport-related proteins as well as with their functional characterization.