Radiation-induced segregation and void formation on grain boundaries in titanium-modified Type 316 stainless steel were investigated by electron irradiation and X-ray microanalysis (EDX). Strong enrichment and depletion of solutes were observed on grain boundaries during irradiation. Moreover, preferential void formation on grain boundaries occurred and grain boundary migration was induced by the irradiation. These facts indicate that grain boundaries act as preferential sinks for radiation-induced point defects, and the sink behavior may be changed by the development of the segregation under irradiation.