Telomeres are specialized DNA complexes found at the end of all chromosomes. Human, as a member of eukaryotic cells, requires telomeres to maintain the length and the stability of chromosomes. Telomeres lose their non-coding DNA sequence to protect the genetic information on the chromosomes. Shortening of telomeres occurs in most somatic cells after sufficient cell division in a human lifetime. Normal haemopoietic cells or stem cells possess telomerase enzyme to restore telomeres and allow further replication. Telomere dysfunction is the origin of several degenerative disorders and also predispose to cancer. Roles of telomere in carcinogenesis and ageing related disorders are reviewed.