This book presents to students of introductory physical chemistry the basic principles of symmetry and group theory, and their use in describing and predicting molecular structure and spectra. Symmetry is a crucial determinant of many chemical phenomena, and group theory is the grammar of the language of symmetry. In many cases, simple calculations suffice to explain why certain triatomic molecules are linear and others bent, or why certain transitions do not appear in molecular spectra. In this book, the aim is understanding the ideas, and skills in application of the principles, rather than mathematical rigour. The book is intended as a supplement for students who want to follow up an interest in and recognition of the importance of group theory, and who seek a short and mathematically relatively undemanding introduction. Exercises appearing throughout the text are integrated with the presentation to give readers confidence in their assimilation of the material.