1. Introduction The structure and reactivity of radicals. Time scales: the importance of reaction rates. A general comparison with ionic reactions. 2. General Principles: Chain Reactions Based on Stannane Chemistry Keeping the concentration of radical species low: chain reactions. A simple chain reaction based on tin hydride. The Barton-McCombie deoxygenation. Unimolecular and bimolecular steps: the effects of temperature and concentration. Additions to olefins: general considerations. Intramolecular additions: rates, regio- and stereochemistry. Some synthetic applications (including nitrogen and oxygen centred radicals). Intermolecular additions: rates and frontier orbital considerations (polar effects), regio- and stereochemistry. 3. Further Chain Reactions of Stannanes Radical rearrangements. Ring opening: rates, regiochemistry and stereoelectronic effects. Synthetic applications. Migrations of functional groups (aryl, vinyl, nitrile, etc.). Applications to ring expansions and contractions. Hydrogen abstractions: the effects of geometry and polar effects on rates; synthetic applications. Fragmentation processes: general considerations. Allylstannanes and related derivatives. 4. Silicon, Germanium and Mercury Hydrides Silicon and germanium hydrides: general considerations. Tris(trimethylsilyl)silane. Chain reactions with mercury hydrides. 5. Radical Decarboxylations and Related Reactions The Barton decarboxylation reaction: the basic process. An improved Borodin-Hunsdiecker reaction. Further variations. C-C bond formation. 6. Atom and Group Transfer Reactions Kharasch type processes. Degeneracy and the lifetime of the intermediate radicals. Hydrogen atom transfer from thiols and activated C-H bonds. Halogen atom transfer. Transfer of xanthates. 7. Non-Chain Processes The persistent radical effect. Photolysis of nitrites (the Barton reaction). Mimicking vitamin B12: the chemistry of organocobalt derivatives. 8. Redox Processes Electron transfer processes. Generation of radicals by oxidation: general reaction scheme. Oxidations with metal salts (MnIII; CeIV; PbIV; AgII; CuII; FeIII). Combinations of metal salts. Generation of radicals by reduction: general reaction scheme. Reductions with metals and metallic salts (CrII; SmII; TiIII; FeII; CuI).