The measurement of biochemical parameters in epidemiologic studies can contribute to a better understanding of mechanisms of chemical carcinogenesis. Through identification and quantitation of chemicals in tissues or body fluids or through markers of "effective dose" such as DNA adducts, mechanisms of cancer etiology and pathogenesis can be elucidated. Different approaches and the associated methodologic problems are discussed along with examples. As a comprehensive case study, the relationship between aromatic amine exposure and bladder cancer is considered in light of different biochemical aspects which could be the target of epidemiologic studies.