Circulating tumor cells (CTCs) are cancer cells shed by solid tumors into the bloodstream. CTCs have recently emerged as valuable prognostic and predictive cancer biomarkers, providing a non-invasive window into disease biology and progression that can be sampled repeatedly over time from a simple blood draw. Moreover, CTC sampling enables real time tracking of cancer plasticity as tumor cells evolve over time and through progressive lines of therapy, thus elucidating mechanisms of cancer dissemination and identifying new therapeutic targets. As such, CTC characterization holds the promise of enabling real-time molecular phenotyping of individual cancer patients’ tumors at diagnosis and throughout treatment, advancing precision medicine in this important and vast patient group. The USC Norris CTC Research Core is a state-of-the-art, multi-platform facility for the capture and analysis of peripheral blood CTCs. The Core employs a variety of technologies that enrich CTCs for enumeration or molecular characterization. Enrichment is done from blood samples drawn by standard venous puncture from patients. In addition, Dr. Goldkorn’s team has developed mouse xenograft research models using labeled CTCs that can be recovered from the mice.