The purpose of this book is to present the theory of Fourier transforms and related topics in a form suitable for the use of students and research workers interested in the boundary value problems of physics and engineering. The focus of the book is on applications, rather than on the theory itself; thus, the first three chapters are devoted to a general treatment of the fundamentals, but no attempt is made to present the foundation in their most general form. Instead, the main theorems are established for a certain class of functions which is sufficiently wide to embrace most of those which occur in problems in applied mathematics. The last seven chapters cover the uses of the theory in solving boundary and initial value problems in engineering and physics. To make the book accessible to undergraduates beginning the study of theoretical physics, no specialized knowledge of physics is assumed, however a good grounding in advanced calculus is a prerequisite. Each chapter begins with a discussion of the physical fundamentals and the derivation of the basic equations. Moreover, the author has taken special pains to include, in the chapters on basic theory, not only the common properties of the Fourier transforms, but also those of the Mellin, Laplace, and Hankel transforms. Finite transforms, dual integral equations, the Wiener-Hopf procedure, and the properties of the Dirac delta function are also considered in some detail. The physical problems included in the text were carefully chosen for their importance and relevance to the topic under discussion.