A long progression due to the intermolecular vibrations of the 2,3-dihydrobenzofuran dimer is observed in the LIF excitation and fluorescence dip spectra. The origin band of the dimer is red-shifted by about 460 cm −1 from that of the monomer. The geometry of the dimer and its change upon electronic excitation are discussed on the basis of the extraordinarily long progression and the large red-shift observed in this system.