The present invention concerns a method for the detection or monitoring of cancer using a biological sample selected from blood, plasma, serum, saliva, urine from an individual, said method comprising: (a) obtaining DNA from the said biological sample; (b) digesting the DNA sample with one or more methylation-sensitive restriction enzymes; (c) quantifying or detecting a DNA sequence of interest after step (b), wherein the target sequence of interest contains at least two methylation-sensitive restriction enzyme recognition sites; and (d) comparing the level of the DNA sequence from the individual to a normal standard, to detect, prognosticate or monitor cancer.