Tris(2,2'-bipyridyl)ruthenium (II) (Ru(bpy)(3)(2+)) electrochemiluminescence is one of the most successful electrochemiluminescent systems and has broad range of applications. Most analytical applications of tris(2,2'-bipyridyl)ruthenium (II) electrochemiluminescence involve coreactants. We comprehensively review typical coreactants, such as oxalate, persulfate, tripropylamine (TPA), NADH (Nicotinamide adenine dinucleotide, reduced disodium salt), 2-(dibutylamino)ethanol, vitamin C derivatives, alcohols, ketones, nucleic acid, formic acid, formaldehyde, organic acids, amines, hydrogen peroxide, oxygen, hydrazine and relative derivatives. The electrochemiluminescent mechanisms are described correspondingly. Furthermore, some perspectives on coreactants are also discussed. (C) 2012 Elsevier Ltd. All rights reserved.