Records that contain street addresses are often found in database systems that are used to monitor the health transactions of medical patients. Although addresses can be used by humans to establish locations, computer systems require more explicit representations to produce maps and conduct analyses. Geocoding is a process through which records without explicit location identifiers are enhanced by the addition of coordinates or geographic identifiers such as census enumeration units.1 In its most typical form, geocoding takes records with addresses and assigns a latitude and longitude value (or other geographic identifier) to each. The purpose of this chapter is to describe the materials that are used to support geocoding, to illustrate geocoding methods, and finally to sketch the types of errors often encountered. An awareness of error types is valuable when attempting to ensure that the results of geocoding are accurate. This has implications for quality control and assurance as well as project management.