Preface to the First Edition. Preface to the Second Edition. 1. Introduction. 2 Force Field Methods. 3. Electronic Structure Methods: Independent-Particle Models. 4. Electron Correlation Methods. 5. Basis Sets. 6. Density Functional Methods. 7. Valence Bond Methods. 8. Relativistic Methods. 9. Wave Function Analysis. 10. Molecular Properties. 11. Illustrating the Concepts. 12. Optimization Techniques. 13. Statistical Mechanics and Transition State Theory. 14. Simulation Techniques. 15. Qualitative Theories. 16. Mathematical Methods. 17. Statistics and QSAR. 18. Concluding Remarks. Appendix A. Notation. Appendix B. B.1 The Variational Principle. B.2 The Hohenberg-Kohn Theorems. B.3 The Adiabatic Connection Formula. Appendix C. Atomic Units. Appendix D. Z-Matrix Construction. Index.