Absorption changes of reaction centers from Rhodospirillum rubrum at 748, 796 and 870 nm induced by 532 and 870 nm picosecond light pulses were investigated with a picosecond spectrometer. Kinetics of absorption changes at 748 and 796 had an additional bleaching when induced by the 532 nm pulse, in comparison with those at 870 nm. The additional bleaching was interpreted as a result of the excitation energy transfer via spectral forms of pigments of reaction centers. The experimental results fit the mathematical simulation of the additional bleaching for the following set of rate constant values: intrinsic conversion to the lowest excited singlet state in bacteriopheophytine molecule--10(13) s-1, energy transfer from bacteriopheophytine to P800 3.10(12) s-1, from P800 to P870--2.10(12) s-1.