PMCID: PMC4636053.-- et al. ; Clear cell renal carcinomas (ccRCCs) can display intratumor heterogeneity (ITH). We applied multiregion exome sequencing (M-seq) to resolve the genetic architecture and evolutionary histories of ten ccRCCs. Ultra-deep sequencing identified ITH in all cases. We found that 73-75% of identified ccRCC driver aberrations were subclonal confounding estimates of driver mutation prevalence. ITH increased with the number of biopsies analyzed, without evidence of saturation in most tumors. Chromosome 3p loss and VHL aberrations were the only ubiquitous events. The proportion of C>T transitions at CpG sites increased during tumor progression. M-seq permits the temporal resolution of ccRCC evolution and refines mutational signatures occurring during tumor development. ; C.S. and M. Gerlinger are supported by grants from Cancer Research UK Biomarkers and Imaging Discovery and Development Committee (BIDD), the Medical Research Council and the Seventh European Union Framework Programme, and C.S. is supported by the Breast Cancer Research Foundation and the Rosetrees Trust. We acknowledge the Ramón y Cajal program of the Ministerio de Economía y Competitividad, Spain, and Novartis for funding support for E-PREDICT clinical trials. This study was supported by researchers at the National Institute for Health Research Biomedical Research Centres at University College London Hospitals and at the Royal Marsden Hospital. ; Peer Reviewed