This statement was prepared by an ad hoc committee on the Society for Research on Biological Rhythms, consisting of Lawrence P. Morin (Chair), Mark S. Bauer, John Dark, Donald I. McEachron, and Herbert Underwood. Dr. Charles C. Middleton, DVM, also assisted in the preparation of this report. This report represents the position of the Society with respect to the care and well-being of animals that are used in experiments involving the study of biological rhythms. The Executive Committee of the Society determined that such a report was necessary, because many experiments involving the study of biological rhythms require special husbandry and housing requirements that are often unique to such studies. Although National Institutes of Health (NIH) and U.S. Department of Agriculture (USDA) guidelines for housing animals are appropriate for animals not in experiments, quite often it is necessary to house animals under experimental conditions for many months in biological rhythms studies, and normal, routine care of these animals could interfere with and perhaps ruin the experiments. The report makes recommendations regarding cages, environmental chambers, rooms, recording devices, observing animals, cleanliness, feeding, lighting, temperature, ventilation, humidity, and safety alarms. The successful completion of experiments on biological rhythms in animals often requires special handling and care of animals on a day-to-day basis. Following the guidelines in this statement should enable investigators to collect meaningful data on biological rhythms, while at the same time ensuring that the animals are maintained in a healthy state and that they receive proper care. —Fred W. Turek, Past President, Society for Research on Biological Rhythms. © 1993, Sage Publications. All rights reserved.