Organocopper(I) compounds and organocuprates are very versatile reagents the use of which in organic syntheses is in many cases advantageous over that of the usual organometallic compounds. Organocopper(I) compounds and organocuprates have been studied mainly in the last decades and years, respectively. Their use in preparative chemistry is still based on empirical facts and the reaction mechanisms have hitherto been relatively little studied. In this survey, the preparation and reactions of organocopper(l) compounds and organocuprates are discussed. The emphasis is on the conditions that influence the course of the reactions. The choice of the solvent and the addition of salts or complexing agents, as well as the nature of the reaction components play an important role. 1. Organocopper(I) Compounds, Pure or in the Presence of Salts 1.1. Alkylcopper Compounds 1.1.1. Preparation, Stability, and Coupling 1.1.2. Reactions with Carboxylic Acid Chlorides and Halogen Derivatives 1.1.3. 1,4-Additions 1.1.4. Perfluoroalkylcopper Compounds 1.2. Arylcopper Compounds 1.2.1. Preparation and Stability 1.2.2. Reactions with Carboxylic Acid Chlorides and Halogen Derivatives 1.2.3. Reaction Intermediates 1.2.4. 1,4-Additions 1.2.5. Perhaloarylcopper Compounds 1.3. Vinylcopper Compounds 1.4. Alkynylcopper Compounds 1.4.1. Preparation and Stability 1.4.2. Reactions with Carboxylic Acid Chlorides 1.4.3. Reactions with Allyl and Propargyl Halides 1.4.4. Reactions with Aryl and Vinyl Halides 1.4.5. Reactions with 1-Halo-1-alkynes 1.5. Cyclopentadienylcopper 1.6. Conclusion 2. Homocuprates 2.1. Preparation and Stability 2.2. Coupling 2.3. Reactions with Carboxylic Acid Chlorides 2.4. Reactions with Allyl and Propargyl Halides and Esters 2.5. Reactions with Haloarenes and Haloalkenes 2.6. Reactions with Haloalkanes and Halocycloalkanes 2.7. Reactions with Oxiranes 2.8. Reactions with Ketones and 1,4-Additions 2.9. Conclusion