Unreinforced masonry infill walls have been frequently used as interior partitions and exterior walls in RC moment frame structures in Korea for a long time. In the seismic design and evaluation of RC moment frames, the masonry infill walls have been usually treated as non-structural elements and ignored in analytical model. In this study, the parametric nonlinear static (pushover) analyses and experimental tests are performed on RC frame with/without unreinforced masonry infill walls. The effects of column shear strength, beam-column stiffness ratios and the amount of axial force applied on the column, are investigated in numerical analyses. Numerical analysis and experimental results indicate that the masonry infill increases the stiffness and strength, but reduces ductility.