The conduct of a clinical investigation of a medical device to determine the safety and effectiveness of the device is covered by the investigational device exemptions (IDE) regulation. The purpose of IDE regulation is "to encourage, to the extent consistent with the protection of public health and safety and with ethical standards, the discovery and development of useful devices intended for human use, and to that end to maintain optimum freedom for scientific investigators in their pursuit of this purpose." Conducting a clinical investigation may require an approved IDE application. The US Food and Drug Administration encourages early interaction with the agency through the pre-IDE approval process during the development of a device or technology and during the preparation of an IDE application. This facilitates approval of the IDE application and progression into the clinical investigation. This paper reviews the terminology and applicability of the IDE regulation and the type of study that requires an IDE application to the Food and Drug Administration. The pre-IDE approval process and the development of an IDE application for a significant risk study of a cardiovascular device are discussed.