This chapter describes the basic categories for regulatory approval to sell/market a molecular profiling technology. The US Food and Drug Administration regulates and provides guidance, for marketing in vitro diagnostic devices (IVD). Three different paths currently exist for obtaining Food and Drug Administration (FDA) approval of an IVD: (a) If the new test can be shown to be substantially equivalent to an existing predicate test on the market, then the 510(k) is the regulatory path for new device approval. (b) If your new diagnostic technology cannot be considered substantially equivalent to an existing technology, and will be used to make a critical medical decision concerning the diagnosis, treatment, or medical management, then the premarket approval (PMA) is the regulatory path of choice. (c) If no predicate device exists and the test is of low or moderate risk, it may be eligible for a de novo reclassification. If the test is done "in house," in the designated laboratory only, for a patient sample that is sent to the laboratory from an outside physician's office or medical facility, then the test can be potentially marketed under "home brew" guidelines (also known as laboratory developed tests) regulated under the Clinical Laboratory Improvement Amendments (CLIA). The Centers for Medicare and Medicaid Services (CMS) assumes primary responsibility for financial management operations of the CLIA program, but the categorization of commercially marketed in vitro diagnostic tests under CLIA is the responsibility of the FDA. Definitions, guidelines, information sources, and instructions for data requirements are outlined for each regulatory pathway.