An experimental investigation of the influence of grain boundaries on the recombination of photogenerated minority carriers in polysilicon is reported here. Spatial dependence of photoconductance across an isolated grain boundary was utilized to evaluate the diffusion length of electrons in the grain and the interfacial recombination velocity. Intensity dependence of these parameters provided some insight into the modulation of the grain boundary potential barrier under illumination. Photoconductance was found to vary with photon flux as Gr, where r=1.0 in regions of the grain far away from the boundary and r=0.4 at the grain boundary plane. The barrier height and electron capture cross section in the grain boundary traps were obtained to be 0.12 eV and 1.16 × 10-16 cm2, respectively.