Many existing reinforced concrete (RC) frame structures that had designed and constructed in Korea before 1997 do not meet the current seismic design requirements set forth by the Korea Building Code and have an inadequate safety assessment. For those structures constructed with insufficient strength and ductility, the required stiffness was also not provided. The frames of these structures have been designed to resist only gravity loads or gravity and moderate lateral loads and do not have proper reinforcement details needed to ensure ductile behavior. In this study, to improve the seismic capacity of masonry walls, hexagonal blocks were developed and the influence of masonry infilled wall on the seismic performance of RC frames that were designed in accordance with current code provisions were investigated. Four 1/2 scale, single story, single bay, frame specimens were tested. The parameters included that the strength of infilled walls using hexagonal blocks with respect to that of the reinforcemet and lateral load history were investigated. The experimental results were shown that infilled wall could significantly improve the performance of RC frames. The lateral loads developed by the infilled frame specimen were higher than that of the bare frame. It also were indicated that reinforced hexagonal block infilled walls could be potentially used to improve the performance of existing nonductile frames.