This handbook on group theory is geared toward chemists and experimental physicists who use spectroscopy and require knowledge of the electronic structures of the materials they investigate. Accessible to undergraduate students, it takes an elementary approach to many of the key concepts. Rather than the deductive method common to books on mathematics and theoretical physics, the present volume introduces fundamental concepts with simple examples, relating them to specific chemical and physical problems. The text is centered on detailed analysis of examples. Since neither chemists nor spectroscopists require theorem proofs, very few appear here. Instead, the focus remains on the principal conclusions, their meaning, and their use. In keeping with the text's practical bias, the main results of group theory are presented in all sections as procedures, making possible their systematic and step-by-step-application. Each chapter contains problems that develop practical skill and provide a valuable supplement to the text.