Werner's syndrome is a typical progeroid syndrome with many specific features of aging early in life. Clinical features of Werner's syndrome closely resemble accelerated aging, such as cataract, scleroderma skin, diabetes and tumorigenesis. The causative gene of this syndrome is denoted as WRN, which encodes a homolog of the E. coli RecQ DNA helicase and is located on chromosome 8p2-p11.2. WRN is not only a helicase but also an exonuclease and ATPase. WRN protein plays a key role in genome stability, particularly during DNA replication and telomere metabolism. In this review, we introduce the clinical characteristics of Werner's syndrome and recent topics concerning WRN in comparison with other progeroid syndromes.