The fate of chemicals in the environment is largely dependent upon microbial biodegradation, or a lack thereof. Biodegradation derives from the extremely broad types of metabolic reactions catalyzed by microbes. Diverse microbial metabolism is represented in the University of Minnesota Biocatalysis/Biodegradation Database (UM-BBD), which is freely available on the Web. The UM-BBD encompasses metabolism of 60 organic functional groups. On average, there are four reaction types for each functional group. Each of these reaction types underlies a metabolic rule. Metabolic rules have formed the basis of a computational system used to predict the biodegradative pathways of chemicals. Many pathways may be predicted. To deal with pathway combinatorial explosion, a rule-prioritization system has been implemented. Additional tools are under development to better understand the underlying characteristics of biodegradative metabolism with the hope of improving biodegradation prediction.