The flexural and shear behavior of reinforced masonry shearwalls subject to both monotonic and cyclic lateral loads is examined. The study is based on the experimental results obtained from more than twenty 6 x 6 ft reinforced masonry wall panels tested under in-plane vertical and lateral loads. For the square wall panels studied, the shear strength is initially provided by the diagonal compression strut mechanism, and later by the interface shear as well as the resistance of the horizontal reinforcement. A simple shear formula, based on the latter and proposed in a prior study, appears to be reliable. In general, wall panels that failed shear exhibited a more brittle behavior than those that failed in flexure. Furthermore, based on experimental data, an empirical formula governing the degradation of shear strength under cyclic displacement reversals is developed.