Addressing both physical and mathematical aspects, this self-contained text on boundary value problems is geared toward advanced undergraduates and graduate students in mathematics. Prerequisites include some familiarity with multidimensional calculus and ordinary differential equations. A brief introductory section precedes the two-part treatment, which begins with coverage of basic theory. Topics include Fourier series of periodic functions, linear boundary value problems, diffusion problems related to the heat equation, steady-state problems involving the potential equation, and propagation problems incorporating the wave equation. The second part focuses on extensions, exploring general second-order linear equations and systems, series methods, integral transform methods, and Sturm–Liouville problems. Problem sets appear throughout the text, along with a substantial section of answers to selected problems. This corrected edition includes a new Preface and an updated Appendix.