The absorption spectra of charge-transfer excited states and one-electron-reduced states of a number of mono- and binuclear ruthenium complexes in water have been obtained using laser flash photolysis and pulse radiolysis techniques. For Ru(dhp)(3)(+)*, the absorption bands are assigned by comparison with Ru(bpy)(3)(+)*. The spectra obtained for Ru(dpp)(3)(+)* and Ru(dpq)(3)(+)* are similar to their respective ground-state absorption spectra. Bimolecular rate constants for the reaction of e(aq) with the above complexes as well as with the mixed-ligand complexes Ru(bpy)(2)dpp(2+) and Ru(bpy)(2)dhp(2+), were also determined. From their characteristic absorption spectra and the bimolecular rate constants, it was concluded that the added electron is localized on one of the ligands. The excited-state absorption spectra of the two mixed-ligand complexes showed bands at 360 and 450 nm attributed to pi-pi* transitions of the ligand anion radical. The lifetimes of the excited states of the complexes decreased on changing the solvent from acetonitrile to water. It was also observed that the lifetimes of the excited states of the binuclear complexes were shorter than those of the corresponding mononuclear complexes.