The semi-empirical topological index (I(ET)), developed to predict the chromatographic retention of a series of organic compounds, is extended to predict other properties and biological activities of aliphatic alcohols. This topological index takes into account the contribution of each individual atom type to the property considered and is able to encode information about structural features of the molecules. The efficiency of this index is verified by high quality Structure - Property and structure - Activity Relationships (QSPR/QSAR) models obtained for several representative physicochemical properties, biological activities and toxicities of aliphatic alcohols. Most of the properties investigated are well modeled (r > 0.98) employing the I(ET). Cross-validation using the more general leave-one-out method demonstrates that these models are highly statistically reliable. The proposed I(ET) index promises to be a useful descriptor in the QSPR/QSAR studies.