DNA methylation was investigated in the putative promoter region of the human dopamine D2 receptor gene (DRD2). Twenty-two DNA samples from two types of cells differentially expressing D2 receptors, striatum and lymphocytes, were subjected to bisulphite modification-based mapping of methylated cytosines. In the tested region, the DNA from lymphocytes exhibited a significantly higher degree of methylation than that from striata. In addition, a significantly higher proportion of methylated to unmethylated cytosines was detected in DRD2 from the right than the left striatum, and a trend towards a greater degree of methylation was detected in older than in younger individuals. These DRD2 methylation findings are consistent with dopamine D2 receptor binding data from the literature which support the idea that DNA methylation plays a role in regulation of DRD2 expression.