An important aim in cancer management is to obtain a detailed molecular portrait of an individual’s tumour and be able to use this information to provide a personalised treatment approach that is more targeted, has superior efficacy and is associated with less toxicity.  Our increasing understanding of the genomic landscape of human tumours and the rational development of biomarkers that can translate this information into the clinic are key to achieving this aim.  The ability to identify and quantify cell-free circulating tumour DNA (ctDNA) in the bloodstream of patients with cancer is opening up new opportunities for noninvasive molecular disease monitoring in several malignancies.  Circulating tumour-derived nucleic acids harbor the somatic genomic alterations found in a patient’s tumour, thus serving as a highly specific cancer biomarker. Recent technological advances are providing new prospects to employ ctDNA in various facets of cancer diagnostics and management.  Clinical applications of ctDNA analysis include monitoring treatment response, detecting early recurrence and identifying emerging treatment resistance, and these approaches are likely to expand in coming years as the analysis of ctDNA using next-generation sequencing evolves.  I will present an overview of recent developments in ctDNA biomarker research and its potential to facilitate personalised treatment approaches.