FDA has a well developed and well defined regulatory program for both drugs and diagnostics. While the use of diagnostic biomarkers for selecting or dosing drugs is not new, recent advances in genomics and in molecular diagnostic technologies have moved interest in biomarkers to the front burner. FDA views the use of biomarker diagnostics as an important component of its new Critical Path initiative, an agency-wide effort to ensure rapid transfer of innovative products from the research bench to the clinical bedside. FDA is developing guidance and refining its regulatory tool box. Our goal is to ensure we work as a partner rather than an obstacle in promoting the development of cutting edge new medical products.