Stilbene radical anions (St(.-)) in the second excited doublet state generated by a pulse radiolysis-laser flash photolysis combined method undergo unimolecular isomerization from c-St(.-) to t-St(.-), photoelectron ejection, and electron transfer to biphenyl added as a quencher. From the selective electron transfer from the St(.-) D-2 states to biphenyl (Bp), k(Bp)tau = 10.7 and 17.8 M(-1) were obtained where k(Bp) and tau denote the rate constants of the electron transfer and the lifetimes of the c-St(.-) add t-St(.-) D-2 states, respectively. The tau values are estimated to be approximately 1.5 +/- 0.4 ns and 2.5 +/- 0.7 ns for the c-St(.-) and t-St(.-) D-2 states, respectively, from k(Bp)tau assuming the diffusion-controlled rate constant for k(Bp). The shorter tau of the c-St(.-) D-2 state is attributed to isomerization via twisting about the central C=C double bond. The tau values of the c-St(.-) and t-St(.-) D-2 states are 1 order of magnitude longer than those of c-St(.+) and t-St(.+) D-2 states. The transient phenomena of the D-2 states of c-St(.-) and t-St(.-) are discussed in terms of their lifetimes, structures, energies, and reaction processes.