On June 1, 2011, the Office of In Vitro Diagnostics (OIVD) in the Food and Drug Administration’s (FDA) Center for Devices and Radiological Health and the Center for Biologics Evaluation and Research issued the first of several anticipated guidance documents intended to clarify the regulation of clinical diagnostic tests and related items. The draft guidance, which is entitled “Commercially Distributed In Vitro Diagnostic Products Labeled for Research Use Only or Investigational Use Only: Frequently Asked Questions” (the Guidance), clarifies FDA’s regulations for labeling and marketing “research use only” (RUO) and “investigational use only” (IUO) tests. The Guidance will apply to reagents, instruments and systems intended for use in the collection, preparation and examination of human specimens in order to diagnose disease or other conditions, including a determination of the state of health. Although it is directed toward manufacturers and distributors of RUOs and IUOs and anyone else who labels in vitro diagnostic (IVD) products, the Guidance may indirectly affect laboratory developed tests (LDTs) and other IVDs that incorporate RUOs or IUOs.