Activity coefficients for the NaI + maltose + water system at 298.15K were determined by an electrochemical method. The Gibbs energy interaction parameter (g(ES)) and salting constant (k(S)) have also been calculated. Infinite dilution apparent molar volumes for maltose (V-Phi,V-S) in aqueous NaI solution and those for NaI (V-Phi,V-E) in aqueous maltose solution have been determined from density measurements as well as volumetric interaction parameters. The results are discussed in terms of the structural interaction model and the structural properties of anions.