A method of determining whether a given single nucleotide is methylated or not methylated characterized by the steps of (a) contacting the single nucleotide with one or more hybridization probe types each of which in its unused form; (b) for the relevant probe type causing (i) the single nucleotide to bind to the region resistant to exonucleolytic degradation and the single-stranded region and (ii) the second oligonucleotide to bind to the single nucleotide and the single-stranded nucleotide region; (c) treating the used probe with a methylation-dependent restriction or a methylation-sensitive restriction endonuclease to cleave adjacent the region resistant to exonucleolytic degradation; and thereafter (d) treating the product of step (c) with an exonuclease or a polymerase exhibiting exonuclease activity to liberate either only first or both first and second detectable elements in a detectable state to determine if the single nucleotide is methylated or not.