Werner syndrome (WS) is a hallmark premature aging disease, in which the patients appear much older than their chronological age, and exhibit many of the clinical signs and symptoms of normal aging at an early stage in life. They develop many age-associated diseases early in life including atherosclerosis, osteoporosis, cataracts and display a high incidence of cancer. WS is also marked by increased genomic instability, manifested as chromosomal alterations. Characterization and study of the Werner protein (WRN) suggests that it participates in several important DNA metabolic pathways, and that its primary function may be in DNA repair processes. Thus, the WRN protein represents an important link between defective DNA repair and the processes related to aging and cancer.