In many large genetic studies, the amount of available DNA can be one of the criteria for selecting samples for study. In the case of large population cohorts, selecting samples based on their DNA yield can lead to biased sample selection. In addition, many valuable clinical and research sample collections exist in which the amount of DNA is very small. Unbiased whole genome amplification (WGA) of such unique samples enables genomewide scale genetic studies that would have been impossible otherwise. Multiply primed rolling circle amplification (MPRCA) and multiple displacement amplification (MDA) methods are based on the same principle. The DNA amplification is non-PCR based and uses Φ29 DNA polymerase and random hexamer primers for unbiased whole genome amplification. MDA is used for linear DNA molecules, such as genomic DNA. This chapter reviews the various applications in which whole genome amplified DNA can be used, the types of commercial kits available, and the quality control steps necessary before using the DNA in the genetic studies.