A real-time method of detecting the presence and/or amount of a methylated or unmethylated gene of interest in a DNA-containing sample, comprises the steps of: (a) contacting the DNA-containing sample with a reagent which selectively modifies unmethylated cytosine residues in the DNA to produce detectable modified residues but which does not modify methylated cytosine residues (b) amplifying at least a portion of the methylated or unmethylated gene of interest using at least one primer pair, at least one primer of which is designed to bind only to the sequence of methylated or unmethylated DNA following treatment with the reagent, wherein at least one primer in the primer pair produces a detectable fluorescence signal during amplification which is detected in real-time (c) quantifying the results of the real-time detection against a standard curve for the methylated or unmethylated gene of interest to produce an output of gene copy number.