From the Cancer Research UK Lung Cancer Centre of Excellence (M.J.-H., G.A.W., N. McGranahan, N.J.B., S.V., S.S., D.H.J., R.R., S.-M.L., M.D.F., C.A., S.M.J., C.D., C.S.), London and Manchester, Good Clinical Laboratory Practice Facility, University College London (UCL) Experimental Cancer Medicine Centre (H.L.L., J.A.H.), Bill Lyons Informatics Centre (J.H.), and Cancer Immunology Unit (S.A.Q.), UCL Cancer Institute, the Translational Cancer Therapeutics Laboratory (G.A.W., N. McGranahan, N.J.B., T.B.K.W., A.R., T.C., S. Turajlic, H.X., C.T.H., C.S.), Department of Bioinformatics and Biostatistics (R.M., M.S., S.H., M.E., A.S.), Advanced Sequencing Facility (N. Matthews), and Cancer Genomics Laboratory (S.D., P.V.L.), Francis Crick Institute, the Renal and Skin Units, Royal Marsden Hospital (S. Turajlic), the Departments of Medical Oncology (M.J.-H., S.-M.L., M.D.F., T.A., C.A., C.S.), Pathology (M.F., E.B., T.M.), Cardiothoracic Surgery (D.L., M.H., S. Kolvekar, N.P.), Respiratory Medicine (S.M.J., R.T.), and Radiology (A.A.), UCL Hospitals, Lungs for Living, UCL Respiratory, UCL (S.M.J.), the Department of Radiotherapy, North Middlesex University Hospital (G.A.), the Department of Respiratory Medicine, Royal Free Hospital (S. Khan), and UCL Cancer Research UK and Cancer Trials Centre (N.I., H.B., Y.N., A.H.), London, Cancer Studies, University of Leicester (D.A.M., D.A.F., J.A.S., J.L.Q.), the Department of Thoracic Surgery, Glenfield Hospital (A.N., S.R.), and the Medical Research Center Toxicology Unit (J.L.Q.), Leicester, the Institute of Cancer Studies, University of Manchester (F.B.), the Christie Hospital (F.B., Y.S.), the Departments of Cardiothoracic Surgery (R.S.) and Pathology (L.J., A.M.Q.) and the North West Lung Centre (P.A.C.), University Hospital of South Manchester, and Cancer Research UK Manchester Institute (C.D.), Manchester, the Departments of Thoracic Surgery (B.N.) and Cellular Pathology (G.L., S. Trotter), Birmingham Heartlands Hospital, Molecular Pathology Diagnostic Services, Queen Elizabeth Hospital (P.T., B.O.), and Institute of Immunology and Immunotherapy, University of Birmingham (G.M.), Birmingham, the Departments of Medical Oncology (M.N.), Cardiothoracic Surgery (H.R.), Pathology (K.K.), Respiratory Medicine (M.C.), and Radiology (L.G.), Aberdeen University Medical School and Aberdeen Royal Infirmary, Aberdeen, the Department of Respiratory Medicine, Barnet and Chase Farm Hospitals, Barnet (S. Khan), the Department of Respiratory Medicine, Princess Alexandra Hospital, Harlow (P.R.), the Department of Clinical Oncology, St. Luke’s Cancer Centre, Guildford (V.E.), the Departments of Pathology (B.I.), Respiratory Medicine (M.I.-S.), and Radiology (V.P.), Ashford and St. Peters’ Hospitals, Surrey, the Department of Clinical Oncology, Velindre Hospital (J.F.L.), the Departments of Radiology (H.A.) and Respiratory Medicine (H.D.), University Hospital Llandough, the Departments of Pathology (R.A.) and Cardiothoracic Surgery (M.K.), University Hospital of Wales, and Cardiff University (R.A.), Cardiff, and Wellcome Trust Sanger Institute, Hinxton, and Big Data Institute, University of Oxford, Oxford (S.D.) — all in the United Kingdom; the Center for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark, Lyngby (Z.S.); the Computational Health Informatics Program, Boston Children’s Hospital and Harvard Medical School, Boston (Z.S.); MTA-SE-NAP, Brain Metastasis Research Group, 2nd Department of Pathology, Semmelweis University, Budapest, Hungary (Z.S.); Berlin Institute for Medical Systems Biology, Max Delbrueck Center for Molecular Medicine, Berlin (R.F.S.); and the Department of Human Genetics, University of Leuven, Leuven, Belgium (P.V.L.). Address reprint requests to Dr. Swanton at the Translational Cancer Therapeutics Laboratory, Francis Crick Institute, 3rd Fl. SW, 1 Midland Rd., London NW1 1AT, United Kingdom, or at charles.swanton@crick.ac.uk.A complete list of investigators in the Tracking Non–Small-Cell Lung Cancer Evolution through Therapy (TRACERx) Consortium is provided in Supplementary Appendix 1, available at NEJM.org.