Since 1961 the author has taught a course in Cytogenetics at Montana State University. Undergraduate and graduate stu- dents of Biology, Chemistry, Microbiology, Animal and Range Science, Plant and Soil Science, Plant Pathology and Veterinary Science are enrolled. Therefore, the subject matter has been pre- sented in an integrated way to correlate it with these diverse disciplines. This book has been prepared as a text for this course. The most recent Cytogenetics text was published in 1972, and rapidly developing research in this field makes a new one urgently needed. This book includes many aspects of Cytogenetics and related fields and is written for the college student as well as for the researcher. It is recommended that the student should have taken preparatory courses in Principles of Genetics and Cytol- ogy. The content is more than is usually taught during one quar- ter of an academic year, thus allowing an instructor to choose what he or she would like to present to a class. This approach also allows the researcher to obtain a broad exposure to this field of biology. References are generously supplied to stimulate orig- inal reading on the subject and to give access to valuable sources. The detailed index is intended to be of special assistance to researchers.