For many years statistics has been regarded as the essential mathematical preparation for biologists. Recently, however, it has become necessary to broaden this background to include advanced techniques such as linear differential equations. The difficulty with this has been that most courses in differential equations are designed for engineering students. This book is designed for biologists. It was developed in a graduate course at the University of Rochester School of Medicine but the approach is such that it will be useful at either the undergraduates or the graduate level.