‘Companion diagnostics’ is a term that’s been in the news recently as more drug/big pharma and diagnostic developers partner to focus on technical/scientific advances in predictive biomarker identifications and development and subsequent commercialization. And heavy hitters like Siemens, Roche, Vantana, Pfizer and GlaxoSmithKline, to name only a few, are leading the way. This means that as their partnerships and progress continue, better clinical laboratory assays will result and patients will be diagnosed and treated more expediently and effectively. In fact, the 5th World Companion Diagnostics Summit—to be held next March in Germany—is designed to bring all these leaders together to ensure advancement continues at an appropriate pace. While companion diagnostics has promise to expedite the development process, several questions need to be answered. Leaders at the summit plan to address, for example, how to translate treatment stratification markers from bench to bedside and move from research grade assay toward a clinically useful diagnostic test. As such, should you invest in in-house development or outsource? Should you develop LDTs or IVDs? What are the benefits and challenges associated with both prospective and retrospective biomarker development and in defining biomarker positive and negative patient populations? Stay tuned.