This is an undergraduate textbook on basic pharmacological principles and the general concepts of chemical-biological interactions. The book guides the student through the most elementary aspects of pharmacology to a sophisticated understanding of drug mechanisms. Each chapter ends with a summary section and a "Guides for Study and Review", which contains a series of essay-type questions designed to test the student's comprehension of the material in the chapter. This edition includes updates and two-colour printing of the illustrations for clarification of key concepts.