note that concordance of target organ effects in animals and humans was not a requirement in evaluating the implications of animal data for human risk. Site concordance of tumors is usually judged as providing strong evidence of an association, and the committee did consider this relationship in evaluating the data. However, the committee’s review focused on mode-of-action information to understand how trichloroethylene might affect certain processes differently in different species. Chapter 9 discusses susceptibility to trichloroethylene and its metabolites, and Chapter 10 describes important factors in considering trichloroethylene in mixtures. Physiologically based pharmacokinetic models are evaluated in Chapter 11, and guidance is provided on future directions for model development. Finally, Chapter 12 considers issues related to dose-response assessment and quantitative assessment of risk.