Nitrones readily undergo cycloaddition reactions with a wide variety of carbon-carbon, carbon-nitrogen, carbon-sulphur, carbon-phosphorus, nitrogen-sulphur, and nitrogen-phosphorus multiple bond systems to produce various heterocyclic five-membered ring systems. The nitrones are simple derivatives of carbonyl compounds so that the reaction sequence -conversion of a carbonyl compound (mostly aldehydes) to a nitrone, formation of the five-membered ring system, and final decomposition of the cyclo-adduct provides a route to new carbonyl compounds. 1. Introduction 2. Addition to Carbon-Carbon Bonds 2.1. Alkynes 2.2. Benzyne 2.3. Alkenes 2.4. Allenes 2.5. Ketenes and Ketene Imines 3. Addition to Carbon-Nitrogen Bonds 3.1. Nitriles 3.2. Isocyanates 3.3. Isothiocyanates 3.4. Carbodiimides 3.5. Aziridinium and Azetidinium Salts 4. Addition to Carbon-Sulphur Bonds 4.1. Carbon Disulphide 4.2. Isothiocycanates 4.3. Thioketenes 4.5. Sulphenes 5. Addition to Carbon-Phosphorus Bonds 5.1. Phosphoranes 6. Addition to Nitrogen-Sulphur Bonds 6.1. N-Sulphinyl Compounds 7. Addition to Nitrogen-Phosphorus Bonds 7.1. Iminophosphoranes