Recognition that most human exposures to environmental chemicals occur as complex mixtures has stimulated research and the development of new methods to assess exposure, dosimetry, and genotoxic effects. New genetic and molecular methods are being applied to each aspect of research to develop new methods for the assessment of cancer risk from human exposure to complex mixtures. Short-term genetic bioassay methods utilizing new engineered bacterial strains are being used to assess total human exposure to mutagens in the environment. New DNA adduct methods are being used in exposure-dosimetry studies of complex mixtures in humans and in experimental systems. Finally, new advances in sequencing the genetic mutations induced by environmental mutagens will improve our understanding of the relationship between DNA adducts, DNA damage and repair, mutation induction, and tumor initiation.