This article provides the background of biological evaluation of medical devices. It discusses what the ISO 10993 standards require for polymeric biomaterials and presents examples of what qualitative and quantitative tests can be used to satisfy the requirements. The article describes infrared (IR) analysis and thermal analyses that are used extensively to fingerprint polymeric materials and should be a part of all polymeric biomaterials characterization programs. It also provides 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 steps include hazard identification, dose-response assessment, and exposure assessment, and risk characterization.