Described is a method for detecting 5-methylcytosine in genomic DNA samples. First, a genomic DNA from a DNA sample is chemically converted with a reagent, 5-methylcytosine and cytosine reacting differently, and the pretreated DNA is subsequently amplified using a polymerase and at least one primer. In the next step, the amplified genomic DNA is hybridized to at least one oligonucleotide, forming a duplex, and said oligonucleotide is elongated by at least one nucleotide, the nucleotide carrying a detectable label, and the elongation depending on the methylation status of the specific cytosine in the genomic DNA sample. In the next step, the elongated oligonucleotides are analyzed for the presence of the label.