Epigenetic silencing in eukaryotes is associated with the formation of a transcriptional repressive higher order chromatin structure which is also characterized by methylation of DNA at cytosine nucleotides. DNA methylation in eukaryotes involves of a methyl group to the carbon -5 position of the cytosine ring (5-mC). This reaction is catalysed by DNA methyltransferase in the context of the sequence 5'-GC-3', which is also referred to as a CpG dinucleotide. Differential methylation of CpG islands has been inversely correlated with gene activity: transcriptionally active genes were found to be hypomethylated, whereas transcriptionally silent genes were hypermethylated (Bird, A. 1992, Razin A. et al., 1991, Singal R., 1999). In our experiments in situ hybridisation technique and high-resolution cytometry were used to determine selected metaphase chromosomes HSA 1, 10, 18, 19 and 20. Sequential 5-methylcytosin (5-mC)-rich regions were visualised on metaphase chromosomes 1,10, 18, 19, and 20 using immunofluorescent labelling. The aim of this work was to study the methylation status at the chromosomal level in different cell types.