1. Electronic Configurations and Physical Properties of the Cyclobutarenes. 2. Methods of Generation of Benzocyclobutene and Related Compounds. 3. The Chemistry of Benzocyclobutene and Related Compounds. 4. Methods of Preparation of Biphenylene and Related Compounds. 5. The Chemistry of Biphenylene and its Derivatives. 6. Substituted Derivatives of Biphenylene. 7. Annelated Derivatives of Biphenylene. 8. Heterocyclic Biphenylenes and their Derivatives. Appendix A. 1 H Nmr data. Appendix B. 13 C Nmr data. Subject index.