This study investigates the effects of transverse reinforcement ratios on the post-elastic performance of diagonally-reinforced coupling beams in coupled core wall systems. Two coupled wall subassemblages, with two different transverse reinforcement detailings, were designed and tested under cyclic reversed loads. The design philosophy for both specimens is presented and discussed, and the detailing is compared with what is required by ACI 318-05. The experimental results are presented, with attention to the post-elastic performance of the specimens tested. Overall performance comparisons are made. Findings show that providing a higher transverse reinforcement ratio in a diagonally-reinforced coupling beam than that currently required by ACI 318-05 greatly benefits ductility and hysteretic stability.