Among the primary goals of a risk assessment are 1) determination of the presence or absence of a cause-effect relationship and 2) quantifying the risk through dose-response analysis. Dose-response data may be derived from in vivo studies in animals or humans, which usually provide the basis for risk characterization, and in vitro studies, which are often related to investigations of mode of action (MOA). MOA information describes key events and processes that would explain the overall process of development of a toxic effect. MOA can also be relevant in considering susceptibility factors within populations and in considering the cumulative effects of exposure to more than a single agent. Over the last several years, advances in our understanding of the ways that chemicals interact with biological systems have yielded several frameworks for evaluating toxicity datasets to determine biologically plausible modes of action and relevance to humans. These frameworks can be used to consider the weight of evidence of hypothesized modes of action in animals and their potential human relevance for both cancer and non-cancer effects. This could result in a move away from defaults to adopt modern knowledge on MOA to improve risk assessments, including the choices for dose-response assessment.