Quaternaryammonium tribromide (QATBs) are highly efficient brominating agents. These reagents are capable of brominating organic substrates without the use of elemental bromine and act as vital reagents for preparation of various kinds of bromoorganics of diverse importance. Regarded as ‘solid bromine’, they are widely used in the bromination of allyl alcohols, enones, alkenes, alkynes, activated aromatics and polycyclic hydrocarbons, among others. They are also used as bifunctional catalysts in the oxidative bromination of aromatic compounds by aqueous hydrogen bromide/hydrogen peroxide, and diastereoselective bromination of allyl glycosides. A volume of work has emerged on Quaternary Ammonium Tribromides and through this book an attempt has been made to focus on the role of these reagents as brominating agents.