This thesis presents the limit analysis of masonry structures under the lateral exposures, that’s the most intentionally given sudden earthquakes and also to the associated lateral forces. The current study here in is concerned firstly on the parametric analysis of masonry walls to the lateral loads. Secondly, the analyses of representative existing masonry walls under lateral exposures are done. A simple user friendly but very important software, named Block, is used for this study. It is based on the rigid block modelling concept. In the parametric part, the basic and immediate first step, it is studied the relation of seismic safety factor with respect to the masonry wall shapes, masonry unit sizes, type of masonry bond, compressive stress and also the effect of overloading in which they are applied for a significant set of masonry two dimensional walls and their associated collapse mechanisms to lateral loads. The software gives the safety factor for a certain masonry structure as a function of the gravitational load of the masonry and the overloads on the masonry that are in the direction of gravity. With this, it was possible to know the relations among safety factor and other parameters.