I Qualitative Valence Bond Theory of Model Systems.- A. The Formal and Conceptual Difficulties of MO Theory.- B. Levels of VB and MO Theories.- C. Qualitative Valence Bond Theory.- D. Physical Interpretation of Diagonal Energy Matrix Elements.- E. Physical Interpretation of the Interactions of CW's: "Ionic" versus "Covalent" Delocalization.- F. Diagrammatic Matrix Elements.- G. The VB Theory of Aromaticity.- H. Heitier - London Theory of Stereoselection.- I. The "Perfect" Form of Heitler - London Theory.- J. Why HL Theory Cannot Qualify as a General Theory of Chemical Bonding.- K. The Transition to "Orthogonal" VB Theory and Its Approximate Variants.- L. The Physical Interpretation of VB Configuration Wavefunctions..- M. Huckel Valence Bond Theory of Stereoselection.- N. Neglect of Differential Overlap Valence Bond Theory of Stereoselection.- O. The Electronic Basis of Stereoselection.- P. Conclusion.- References.- Appendices.- II Qualitative Molecular Orbital-Valence Bond Theory.- A. MOVB Theory.- B. The MOVB Approach to Ground State Stereochemistry.- C. Ground State Bond Diagrams.- D. The Representation of Elementary Systems.- E. The Basic Stereochemical Problems.- F. Selection Rules for Chemical Bonding.- G. The Concept of the Effective Energy Gap.- H. The Representation of Polyelectronic Systems.- I. Core and Ligand Group Orbitals.- J. Applications.- K. Compact MOVB Theory.- L. Epilogue.- References.