A telomere is a repetitive DNA structure capping the chromosomal ends. Telomeres stabilize the chromosome structure and prevent harmful end-to-end recombinations. The telomere length of somatic cells call be determined as (fie terminal restriction fragment length provided by a genomic Southern blotting analysis. and the telomere length becomes shorter at each mitotic cycle due to an "end-replication problem." Therefore, older somatic cells. which have Undergone more mitotic cycles, bear shorter telomeres. This telomere shortening is, accelerated by various disease condition,,,. Parkinson's disease (PD) also yields telomere fragility. thus accelerating, the telomere shortening, of the Circulating leukocytes. This study found that peripheral leukocytes of Japanese PD patients bear fewer short telomeres with constant subtelomeric methylation Status ill comparison with the health), controls With increasing short telomeres and also increasing hypomethylated subtelomeres in short telomeres with aging. The correlation between the telomeric attrition and the subtelomeric methylated state in PD is herein discussed.