A method is described for the detection of the degree of methylation of a specific cytosine in the sequence context 5′-CpG-3′ of a genomic DNA sample. In the first step, the genomic DNA is chemically treated in such a way that the cytosine bases are converted to uracil, but not the 5-methylcytosine bases. Then segments of the genomic DNA which contain the said specific cytosine are amplified, whereby the amplified products are given a detectable label and in the following steps the extent of hybridization of the amplified products on two classes of oligonucleotides is determined by detection of the label of the amplified products, and a conclusion is made on the extent of methylation of said specific cytosine in the genomic DNA sample from the ratio of the labels detected on the two classes of oligonucleotides as a consequence of the hybridization.