A simple, yet quite accurate method for predicting properties of organic compounds of environmental and nutraceutical interest is presented. It is an extension of a previous successful group-contribution method (Constantinou, L.; Gani, R. AIChE J. 1994, 40, 1697) and uses two kinds of groups: first-order groups that describe the basic molecular structure of the compounds and second-order groups, which are based on conjugation theory and improve the accuracy of the predictions. Twenty-six new first-order groups have been defined to ensure that the molecular structures of any compound of biochemical interest, including complex aromatic, multiring, and heterocyclic compounds, can be easily described. Furthermore, 12 new second-order groups have been defined to enhance the reliability of the predictions and the applicability of the method. The three properties that have been estimated by the new method are the octanol-water partition coefficient (logKow), the total (Hildebrand) solubility parameters at 25 degreesC, and the flash point. These properties have many applications in the chemical, pharmaceutical, and food industries, as well as in the protection of the environment.