The invention describes a method for the quantitative sequencing of nucleic acids treated with bisulfite. The invention particularly describes a method for the determination of the degree of methylation of a cytosine in the base sequence 5′-CG-3′, thus in a so-called CpG position, if the genomic sequence of the investigated DNA region is known. The invention makes possible the validation of sequence information in the sequencing of DNA treated with bisulfite. It is particularly described how the data obtained with conventional sequencing methods are first standardized with respect to their signal intensity, how the conversion rate of cytosine to uracil after bisulfite treatment is determined from these data, and how a correction factor can be determined with the help of this conversion rate, and this factor produces an essentially improved estimation of the degree of methylation actually present.