The rural practitioner often sees a patient or community member with concerns about environmental exposure. Many of these exposures have the potential to cause an adverse health effect. However environmental exposures, often chemicals, have properties that may influence the likelihood of causing an acute or chronic illness. Knowledge of these properties will determine how the chemicals may affect the body and will help guide the practitioner in evaluating, treating, and counseling their patients. The basic principles of toxicology will be described so the practitioner can understand how chemicals are absorbed, distributed, metabolized, and eliminated from the body. As our environment is becoming more contaminated the rural practitioner needs to have a basic understanding of how various agencies evaluate the risk to the community. The basic steps of a risk assessment process are described with the goal of decreasing the risk of harm to the community.