This text represents a new entry level course in mathematics for students in programs such as mathematics, the sciences and engineering, which require additional courses in mathematics. With enough material for a two semester course, the text is written at approximately the level of introductory calculus. Principles and Practice of Mathematics was developed over a four year period, under the direction of COMAP, with NSF support. It is an alternative point of entry into the undergraduate mathematics curriculum, one which presents for students a wide spectrum of the contemporary world of mathematics. By emphasizing the breadth and variety of modern mathematical inquiry and applications, the text provides a view of the subject that is not experienced by students in the traditional calculus course. The author team and advisors were selected for their experience with undergraduate education. Among our authors are several who have written successful textbooks. The entire project has evolved under the editorial supervision of veteran COMAP author, Walter Meyer, Adolph University.