Following the performance-based design currently adopted in theTechnical standards for port and harbor facilities in Japan, this paper discusses issues facing the effective utilization of existing caissons. When current design criteria were experimentally applied to caissons in existing breakwaters designed using previous methods, some caisson members were found to not satisfy their required performance. Based on the present maintenance techniques, issues related to performance evaluation of caisson members, repair and reinforcement of a caisson, and ensuring performance throughout the design service period were discussed.