The study presents a strategy for evaluation of biodegradability of chemicals which involves a combination of structure-biodegradation relationships (SBR) and laboratory testing arranged in a four-tier hierarchy. The first tier involves a search of a data base on biodegradation information. Each subsequent tier consists of a query of potential SBR for the chemical or an experimental laboratory test of the chemical using a tier-specific procedure. The approach satisfies the critical need to develop a systematic reference data base on biodegradation endpoints for existing and new chemicals, incorporates the metabolites of biodegradation into the process, and provides an economical means to evaluate chemical biodegradation.