Exposure to genotoxic agents in the environment such as ionizing radiation, UV, and chemical carcinogens leads to DNA damage. Additionally, some endogenous agents derived from cellular metabolism such as reactive oxygen species (ROS) also frequently damage DNA. DNA damage is cytotoxic and genotoxic, which can result in acute cell killing or prolonged deleterious biological effects that include chromosomal aberrations, gene mutations, cancer, neurodegeneration, and aging. Cells contain complex systems in response to DNA damage. Multiple laboratories at the Graduate Center for Toxicology are focused on studies of genotoxicology. Their specific areas of research include base excision repair, nucleotide excision repair, and mismatch repair; translesion DNA synthesis and base damage-induced mutagenesis; resolution of DNA damage-induced replication blockage; molecular basis of repair-deficient human diseases; relationship between DNA damage, mutagenesis, and cancer; role of DNA damage and repair in lung cancer incidence in the Kentucky Appalachian region; and exploring DNA repair and mutagenesis as potential targets for cancer therapy and prevention. Research involves both basic and translational aspects of genotoxicology.