We observed persistent photoconductivity inYBa2Cu3Oxbicrystal grain boundary Josephson junctions. Upon illumination of these grain boundary Josephson junctions, the normal state resistance decreases and the critical current increases. This strongly suggests that the grain boundary in these films consists of oxygen depletedYBa2Cu3Ox.A comparison with the persistent photoconductivity in oxygen depletedYBa2Cu3Oxthin films implies an average oxygen content ofx=6.6±0.1for the grain boundary. The spectral dependence has a lower threshold for persistent photoconductivity in the junctions(≈1.2 eV) than in thin films. ©1997 American Institute of Physics.