Poly(ADP-ribosyl)ation polymerase-1 (PARP-1) is a major factor of DNA repair. Age-related parameters such as body weight and blood cholesterol in knockout male mice PARP-1 were more pronounced as compared with controls. Mean life span was shorter (486 +/- 31.7 and 723 +/- 22.6 days, respectively, (p = 0.000005) while initial risk of death (beta) was 8 times as high as in mice PARP-1(+/+). Mean latency of all tumors in knockout and control mice was 656 +/- 43.5 and 782 +/- 33.8 days, respectively, (p < 0.05). Among the most frequent neoplasms were tumors of the liver (experimental--22% and control--8%, respectively) (p = 0.03) and lungs (8% and 12%, respectively). Hence, mice PARP-1(-/-) revealed certain typical charhacteristics of accelerated aging, shorter life span, earlier carcinogenesis and higher rates of liver tumor incidence as compared with mice PARP-1(+/+). Our evidence highlights the role of DNA repair in carcinogenesis and aging.