Photoexcitation and electron-transfer properties of two series of oligo(thienylene-ethynylene)s, in which thiophene rings were connected with ethynylene groups at 2,5 or 2,3 positions (nalphaTE or nbetaTE; n denotes the number of the repeating unit), have been studied. From MO calculations and steady-state absorption spectra, expanded pi-electron systems were expected for rod-type nalphaTE in the ground states, while limited pi-electron systems were expected for coil-type nbetaTE. On the other hand, because nbetaTE shows a substantial red shift of the fluorescence band similar to that of nalphaTE with increasing n value, a conformational change expanding pi-conjugation of nbetaTE was suggested in the excited state. From the picosecond laser flash photolysis, the time scale for the conformational change was evaluated to be ca. 30 ps. The triplet state properties of nalphaTE and nbetaTE were estimated by means of the nanosecond laser flash photolysis. Furthermore, electron donor abilities of the present oligomers were investigated by studying the photoinduced electron-transfer processes with fullerenes, C-60 and C-70. It was revealed that the present oligomers donate an electron to the triplet excited C-60 or C-70 generating the radical cations and anions of oligomers and fullerene, respectively. The electron-transfer rate constants were as small as 0.07-0.0008 of the diffusion-controlled limit, indicating the longer range electron-transfer processes due to larger size of the oligomers and fullerenes. On the other hand, back-electron-transfer processes proceeded at the diffusion-limiting rate.