This article provides a background to the biological evaluation of medical devices. It discusses what the ISO 10993 standards require for polymeric biomaterials and presents examples of qualitative and quantitative tests that can be used to satisfy these requirements. The article describes infrared (IR) and thermal analyses that are used extensively to fingerprint polymeric materials. It also presents a discussion on the chemical characterization and risk assessment of extracts. Background information on risk assessments of extracts is also included. The four basic steps that are commonly used in the risk assessment process are discussed. These include hazard identification, dose-response assessment, and exposure assessment, and risk characterization.