This focused issue of Translational Cancer Research is guest-edited by Dr. Heidi Schwarzenbach from Department of Tumor Biology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. Written by an international team of renowned experts from Austria, Canada, China, England, France, Germany, Russia, Slovenia, Turkey and USA, the current issue provides an overview on technologies using liquid biopsies and shows their importance as non-invasive, blood-based markers and their potential applications in medicine. The issue does not claim to be an exhaustive study, but highlights most general concepts of liquid biopsies.