Large-scale genome-wide association studies (GWASs) have emerged as a powerful approach to identify genetic polymorphisms that are associated with risk of developing cancer and other complex diseases. Currently, microarrays are the genotype screening technology of choice in GWASs because they permit interrogation of more than one-million single-nucleotide polymorphisms (SNPs) at the same time. Many novel loci and genetic variants have been identified as markers of cancer risk in a series of recent reports. With improvement of microarray technologies, population-based GWASs coupled with more quantitative validation methods are poised to reveal, in a systematic manner, numerous small changes in complex genetic networks that in combination can have a major impact on a patient’s risk of developing cancer. Here, we review recent advancement in GWAS in the search and identification of cancer risk factors.