An Introduction to Biological Rhythms provides an introduction to the subject of biological rhythms. The opening chapters present an overview of biological rhythms, their properties, and clock control, followed by a survey of rhythms in plants and animals. The subsequent chapters cover tidal rhythms and human rhythms; sun-compass, star-compass, and moon compass orientation of animals; the clock control of plant and animal photoperiodism; evidence for external timing of biological clocks; and models and mechanisms for endogenous timekeeping. The book also includes biographical sketches of Dr. Frank A. Brown, Jr., Morrison Professor of Biology at Northwestern University; and Dr. Leland N. Edmunds, Jr., Professor and Head of the Division of Biological Sciences at the Stony Brook campus of the State University of New York. This book is meant for the inquiring student seeking an introduction to the subject and for busy biologists in other fields who want to get a "e;"e;feel"e;"e; for the subject. It can also serve as a basic textbook for the existing biorhythms courses and act as a seed for the inauguration of new courses.