Toxicology Tutor I is the first in a set of three tutorials on toxicology produced by the Toxicology and Environmental Health Information Program of the National Library of Medicine, U.S. Department of Health and Human Servicess. It covers Basic Principles of toxicology and is written at the introductory college student level. The Toxicology Tutors are intended to provide a basic understanding of toxicology as an aide for users of toxicology literature contained in the National Library of Medicine's Chemical and Toxicological databases.  Toxicology Tutor II covers Toxicokinetics while Toxicology Tutor III will pertain to Cellular Effects and Biochemistry.