A compilation of experimental values of the infinite dilution partial molar Gibbs energy, enthalpy, and heat capacity of hydration together with partial molar volumes in water at 298.15 K and 0.1 MPa is presented for aliphatic nitriles and dinitriles. These data are treated in the framework of the first- and second-order group additivity methods. Thermodynamic properties are determined for the first- order CN group and for the following second-order groups: C-(CN)(C)(H)(2), C-(CN)(C)(2)(H), and CN-(C). The relatively long-range dipole-dipole interactions of two terminal nitrile groups require additional corrections, {CN-(CH2)(2)-CN}(corr) and {CN-(CH2)(3)-CN}(corr), for lower dinitriles. New experimental studies of aqueous branched mononitriles and lower dinitriles (particularly propanedinitrile) are required to expand the usefulness and accuracy of group contribution models for aqueous nitriles.