We have measured the time response of luminescence intensity in poly(di-n-hexylsilane) films with the excitation density from 1.2×10 18 to 1.1×10 20 excitons cm −3 at 2K. At 1.1×10 20 cm −3 , we found that the rise time is 1.4±0.5ps and that the decay is nonexponential. The rise time is attributed to the exciton–exciton scattering time in which initially photo-generated excitons at 4eV are scattered to the luminescent states at 3.4eV. The nonexponential decay is ascribed to the bimolecular annihilation of excitons with the rate constant γ 2 of (1.0±0.5)×10 −8 cm 3 s −1 . A microscopic mechanism to explain this large γ 2 is discussed.