Quantitative structure-biodegradability relationships (QSBRs) were established for a set of various organic compounds using autocorrelation components as molecular descriptors. The molecules were described by their size (van der Waals volume), electronegativity, hydrogen bonding donor and acceptor ability and lipophilicity (logP). In addition to the established models for alcohols, ketones, and aromatics, we have elaborated a model for both alcohols and ketones (5-day BOD = 0.06V0+ 1.067 logP- 0.356 (logP)2;n= 29,r= 0.958,s= 0.44,F= 145.6) and another for all the compounds (5-day BOD = 0.065V0+ 0.748 logP- 0.316 (logP)2;n= 43,r= 0.906,s= 0.575,F= 91.2).