A microcalorimetric method has been used to obtain the enthalpic interaction parameters for glycine, alpha-alanine and alpha-aminobutyric acid with sodium iodide in aqueous solutions at 298.15 K. It is found that the values of h(xy) increase, whereas those of h(xxy) and h(xyy) decrease as the hydrocarbon chain increases in length (where x represents the non-electrolyte in pure water, and y the electrolyte in aqueous solution). The results are discussed in view of structural interactions.