A group definition criterion based on Bader's theory of atoms in molecules was used to characterize functional groups in 1-alkanols. Application of the criterion entails calculating the electronic charge density for the conformers of the molecules in the series HO(CH2)(n-1)CH3 (n = 1-5) using ab initio quantum mechanical methods at the HF/6-31G*//6-31G* level. The group definition thus established was validated by analyzing the predictions of the group contribution molecular model of Nitta, Turek, Greenkorn, and Chao for 1-alkanol + n-alkane mixtures, which involved fitting the model parameters to the values of various experimental properties for both the pure products and their mixtures with special attention to the excess properties. The model predictions thus obtained were qualitatively and quantitatively better than those provided by previous applications. The model was found to accurately predict second-order derivatives of the Gibbs free energy. Also, the behavior over wide temperature and pressure ranges was qualitatively reproduced.