The phenomenon of tumors shedding cell-free DNA into the blood has opened exciting opportunities in cancer diagnosis, monitoring, and treatment. Initial applications have focused on “liquid biopsy”, to identify clinically actionable mutations when tissue is not available. More recently, emerging technologies have enabled the accurate assessment of molecular residual disease (MRD) in solid cancers, to enable patient stratification in the adjuvant setting, treatment response monitoring, and recurrence monitoring. These MRD technologies also promise to transform and disrupt clinical research, by enabling new trial designs enriched for MRD-positive patients and new surrogate endpoints based on MRD clearance. In this event, we will explore the various technologies being used for liquid biopsy and MRD assessment, as well as the data and applications with highest potential utility in clinical practice and research.