Human genetic variation data are now publicly available on a large scale, from public and private discovery efforts. Datasets from the International Haplotype Map Consortium and Perlegen Sciences provide a level of knowledge about human genetic variation that is unprecedented. In combination with novel high-throughput genotyping technologies, these new resources will allow cancer prevention investigators to identify in a more precise way which genetic subsets of patients are likely to benefit most from chemoprevention and screening interventions.