Companion Diagnostic development requires the development of two separate components (the compound and the diagnostic) which are linked through the goal of being paired in a single therapy. With the pressures within Pharma for fiscal control, efficient and effective development requires IVD statisticians to understand and accommodate statistical characteristics and operational issues in clinical trials for the companion compound, as well as clinical trial statisticians needing to consider the extra requirements and considerations for regulatory approval of the companion diagnostic. This pairing introduces additional challenges for development, including the myriad combinations of compound/device development maturity and the corresponding program and study designs to accommodate differentially imperfect knowledge on the drug/diagnostic interaction.