Ronald L. Fisher, Jr. is a biology teacher at Whitney Point High School in Whitney Point, NY 13862. He holds a B.A. in biology from New College (Sarasota, FL) and an M.A.T. degree from Colgate University (Hamilton, NY). This article is an adaptation of his master’s thesis. John A. Novak currently is Associate Professor of Biology at Colgate University, Hamilton, NY 13346, where he has taught introductory biology, tropical ecology (in Jamaica, W.I.), entomology, invertebrate zoology, and animal behavior. He holds a Ph.D. in zoology from Washington State University (Pullman, WA) and B.A. and M.A. degrees from Kent State University (Kent, OH). In addition to being author or co-author of many articles in professional journals, he is a freelance photographer with Animals Animals Enterprises. Although biology courses often focus upon the structure and physiology of animals, it is also important for students to appreciate the behavior of animals as complete living entities. Recent trends toward formal inclusion of an animal behavior unit in biology courses are therefore welcomed. Animal behavior studies can stimulate student interest, can draw together such diverse topics as physiology, anatomy, ecology, neurology, and reproduction, and can lead to a deeper appreciation of the complexity of living creatures. An equally important goal in biology courses is for students to understand the nature of scientific investigations. Too often biology is still presented as a set of well established “facts,” and the processes that have been used to arrive at this knowledge are ignored. Only by “hands-on” experience with the scientific method can students appreciate the true nature of science. An experimental fish ethology unit can meet both these needs. Fish are among the few animals whose natural environment can be easily reproduced in the lab, allowing ethological studies within a classroom setting. Thus, students in biology courses can get firsthand experience in conducting scientific research while studying the behavior of a fascinating group of animals. Such a unit is presented here. It involves four experiments to be run by small groups of students. Each requires six working days and should be started on a Friday if interrupted by weekends, since the first day of most of the experiments is a practice session that need not be in sequence with the other days. The experiments have been made as flexible as possible so that they are suitable, with slight adaptations, for a wide range of classes. For high school courses, it is recommended that students be provided with the introduction, materials, and methods sections. College students, on the other hand, might be given only an overview of the problem to be investigated, with specific details of the design being left up to them. Results of the test trials could be used as a teacher’s guide for classroom discussion, but should not be taken rigidly; the whole idea is to have students arrive at their own conclusions through scientific investigation. With the few exceptions noted below, only common laboratory equipment is required. Based on our tests of a wide variety of conditions, we have designed the experiments around particular species and have listed the ideal environment requirements, set-up, and supplies. Each teacher will have to match and adapt the available resources. Likewise, teachers may want to try redesigning the experiments to make use of more convenient species. It is believed that the costs and equipment requirements of this unit, while higher than those of traditional “cookbook” labs, are reasonable when one considers the amount of class time spent on the project and the educational value for the students.