Risk assessment, when applied to living systems, is the process of determining the types and likelihoods of adverse effects that may result from exposure to chemical, biological, or physical hazards. Risk assessment is used as a tool to help set regulations and guidelines to prevent or minimize adverse health effects of long-term exposures to low levels of toxicants. It is also applied to evaluating the safety of pharmaceuticals, to protecting workers exposed intermittently to hazardous materials in the workplace, and to evaluating the potential future consequences of past or current exposures. Most toxicological information used in human health risk assessment comes from in vivo experiments in animals and focuses on the pathological response occurring as a result of exposure to the toxicant. Dose and response data must then be extrapolated between individuals and species and from high to low doses, all of which increase the degree of uncertainty in risk estimates. This presentation provides a general overview of risk assessment, exploring its strengths, weaknesses, and ongoing evolution. The distinction between real and perceived risks is also discussed and is shown to be driven by the extent to which mechanistic information is available and how it is integrated into the risk assessment process. Finally, the presentation explores ways in which pathologists and risk assessors can work more closely to enhance risk assessment's ability to be a defensible tool for evaluating health concerns associated with chronic low-level exposures to toxicants in our environment.