Semiconducting polymer heterostructures with strong two-dimensional quantum confinement of excitons are prepared by self-assembly of two conjugated polymers in binary blends. Exciton confinement effects in the semiconducting polymer quantum wires were observed at room temperature by photoluminescence excitation and photoluminescence spectroscopies and by electric field-induced photoluminescence quenching. Observation of new exciton states, enhanced luminescence, and stability of luminescence at high electric fields (3×106V/cm) confirmed the one-dimensionality of the excitons in the organic quantum wires. ©1997 American Institute of Physics.