Bicyclic amidines, especially DBN and DBU, have recently become of interest, principally because of their use as dehydrohalogenation reagents. The use of these compounds in the introduction of double bonds, as well as in various base-catalyzed reactions, is the subject of this review. 1. Preparation of DBN and DBU 2. Dehydrohalogenation Reactions 2.1. Introduction of One Double Bond 2.2. Introduction of Multiple Double Bonds 2.3. Comparison of DBN and DBU in Dehydrohalogenation Reactions 3. Elimination of Sulfonic Acids 4. Phosphorus Ylids 5. Elimination of Hyponitrous Acid 6. Stereochemical Course of the Elimination Reactions 7. Aldol Condensations 8. Rearrangements 9. Reactions with Aromatic Isocyanates 10. Preparation of Carboxylic Acid Chlorides 11. Acylation of Phenols 12. Catalysts in the Synthesis of Macromolecules