The electrochemical redox behavior of the Cypridina luciferin analogue, 6-(4-methoxyphenyl)-2-methylimidazo[1, 2-a]pyrazin-3(7H)-one (MCLA) has been examined in acetonitrile solutions containing 2,6-lutidine or water using cyclic and hydrodynamic voltammetry and double potential-step chronoamperometry. The conjugate base of MCLA (MCLA(-)) is oxidized in two one-electron steps to the radical species (MCLA(.)) and further to the carbocation species (MCLA(+)). The radical-radical coupling of MCLA(.) yields the corresponding dimer ((MCLA)(2)), which is in equilibrium with MCLA(.). MCLA(+) undergoes the addition of a water molecule to yield a hydroxylated form (MCLA-OH) of luciferinol type. The whole mechanism of the electrochemical redox reactions of MCLA(-) coupled with these chemical reactions has been found to be essentially the same as that proposed for the chemical redox reactions of Cypridina luciferin and its analogues, and in addition the kinetic data. concerning the dimerization of MCLA(.), the dissociation of (MCLA)(2) and the hydroxylation of MCLA(+) have been estimated together with the diffusion coefficient of MCLA(-).