Summary: DNA methylation is known to play an essential role in all biological processes through the repression of transcription and development. Hypermethylation of CpGs in the promoters of tumor suppression gene has been demonstrated to cause the epigenetic silence of these genes and constitutes a common feature of many cancers. In contrast, DNA demethylation is necessary for the epigenetic reprogramming of the genes and involves the processes of many important diseases such as tumor progression. Demethylation of DNA can be either passive or active, or a combination of both. Active demethylation of DNA requires specific demethylase participation such as MBD2. There is only the radio isotopic method currently available for measuring DNA demethylase activity/inhibition, which is time consuming, labor-intensive, and has low throughput and produces radioactive waste. The DNA Demethylase Activity/Inhibition Assay Kit addresses these problems by using a unique procedure to measure DNA demethylase. T