A unified treatment of the limit theory of branching processes, this volume focuses on basics. Courses in analysis and probability are prerequisites for this text, which is appropriate for graduate students and advanced undergraduates. The authors begin with a detailed development of the basic Galton-Watson process, and subsequent treatment of continuous time cases (both Markov and age-dependent) reduces analogous questions to Galton-Watson counterparts whenever possible. Concluding chapters focus on multi-type branching processes and special processes, and complements and problems appear at the end of each section. Essentially self-contained, this treatment enables students to engage in independent research.