Methylation of CpG residues in mammalian genomes is a mechanism of vital importance for many cellular functions, which all relate to gene expression. In this study we describe the identification of a CpG island in the 5'-region of the gene encoding human megalin/LRP-2, a receptor capable of binding multiple ligands, which is involved in the regulation of calcium metabolism. Southern blot analysis and genomic bisulfite sequencing revealed that the CpG island is methylated in a non-expressing cell line, largely unmethylated in an expressing cell line and unmethylated in human parathyroid tissue. In addition, we show that artificial methylation of LRP-2 promoter reporter plasmids leads to strong transcriptional repression, in vitro as well as in transfected cells. No evidence for aberrant LRP-2 gene methylation in parathyroid adenomas, in which the LRP-2 protein is generally down-regulated, was found.