Triplet states of poly(phenylene ethynylene), (PPE)-P-3*, not easily formed by direct photoexcitation, were produced by pulse radiolysis in toluene, along with triplet states of T3PPE having terthiophene end-caps. Intense triplet-triplet absorption maxima, (is an element of 680)((PPE)-P-3*) 9.5 x 10(4) M-1 cm(-1) and (is an element of 780)((T3PPE)-T-3*)) 2.8 x 10(4) M-1 cm(-1) enable identification of these two species, which have triplet energies of 2.12 and 1.77 eV determined in bimolecular energy transfer equilibria. Bleaching of ground-state absorption measures (PPE)-P-3* to be the delocalized over a 1.8-nm length. Triplet states formed in the PPE chains were transported to and trapped by the end caps in a time << 5 ns.