Fluorescence from the excited 1,3,5-trimethoxybenzene radical cation (TMB.+*) coexsisting with 1,4-dicyanonaphthalene radical anion (DCN.-) in acetonitrile was studied by the two-step two-laser excitation technique. The fluorescence intensity observed as a function of the delay time of the excitation pulse relative to generation pulse for TMB.+ indicated the quenching by DCN.- at less than or equal to 220 ns. From the analysis of the fluorescence behavior by the Forster-type energy transfer theory, the distance between TMB.+* and DCN.- during their dissipation after the initial photoinduced electron transfer was estimated as a function of time.