Recent advances in cancer immunotherapy have generated excitement across all fields of oncology, and the pressure to discover and validate robust and predictive immune-oncology biomarkers for patient selection is at an all time high. Many diagnostic and pharmaceutical companies are working hand in hand to deliver biomarker support for clinical trials and patient care. Genomic biomarkers, such as tumor mutation burden and microsatellite instability, as well as cell-based and biomarkers of tumor microenvironment have the potential to guide cancer immunotherapy and improve patient outcomes. Some of these biomarkers are being promoted to companion and complementary tests, which brings about unique regulatory, reimbursement and logistics challenges. Technical and scientific advances as well as business considerations with biomarkers and companion diagnostics for cancer immunotherapy will be discussed at the Immuno-Oncology Stream at Next Generation Diagnostics Summit by major stakeholders including biomarker experts from the biopharmaceutical industry, IVD companies and laboratory medicine.