The method according to the invention concerns in particular a method for the quantification of methylated DNA. For this purpose, the DNA to be examined is first transformed such that unmethylated cytosine is converted to uracil while 5-methylcytosine remains unchanged. Subsequently, the transformed DNA is amplified in the presence of a pair of real-time probes. For this, a probe is constructed, which is specific for the methylated or for the unmethylated state of the DNA, and a probe, which binds methylation-unspecifically to the amplificate. The ratio of the signal intensities of the probes or the CT values allows for the calculation of the degree of methylation of the examined DNA. The method according to the invention is suited particularly for the diagnosis and prognosis of cancer and other diseases associated with a change in the methylation status, as well as, prediction of adverse for side-effects of pharmaceuticals.