This course presents a decision tree for reviewing, planning, evaluating, and approving in situ bioremediation (ISB) systems in the saturated subsurface. It defines site parameters and appropriate ranges of criteria necessary for characterization, testing, design and monitoring of ISB technologies. Contaminants and breakdown products differ, however, many characteristics of a site used to determine the efficacy of ISB, are similar. Once a site has been characterized for ISB efficacy and the contaminants of concern and degradation products have been defined, engineered approaches can be designed, pilot tested and possibly deployed. Similarly, several aspects of ISB are characteristic of all sites, no matter what contaminant is being scrutinized. This training is based on the ITRC document entitled: “Systematic Approach to In Situ Bioremediation: Nitrates, Carbon Tetrachloride & Perchlorate.” The document: (1) describes what information is needed for any ISB evaluation; (2) provides a flow diagram that defines the primary decision points; (3) provides characteristics used to evaluate monitored natural attenuation or enhanced ISB application as remediation options. Examples of how to apply this document, including respective decision trees, for nitrate, carbon tetrachloride, and perchlorate are included.