Organometallic catalysis in aqueous systems is now a very active field or research, both from

an academic and an industrial point of view. The use of transition-metal catalysts in water or

in a two-phase system offers the same advantages as in a usual organic medium. However they

simplify the separation of the catalyst from the products, eventually for its recycling, and this

is very important for large-scale chemical processes. The use of water as the solvent can also

exhibit different selectivities to those shown in an organic medium. A comprehensive review

concerningorganometalliccatalysisinaqueoussolutionispresentedhere, withparticular

emphasis on the application in organic synthesis.