Because of its simplicity, low cost, good physical properties, durability and aesthetic qualities confined masonry is used worldwide for the construction of residential, commercial and industrial buildings during an entire century. Experiences on its behaviour during earthquakes are mostly good. However, in modern building practice it is necessary to supplement the traditional construction methods with corresponding numerical analysis. Considering that it is a composite material of uncertain mechanical properties the design process cannot be based on conventional solutions of the theory of elasticity. It is necessary to carry out experimental tests of entire structures, or its component parts, the walls. The objective of this work is to investigate the behaviour of masonry walls subjected to a horizontal cyclic load in the plane of the wall. After that, on the basis of experimental data the numerical simulation of buildings should be carried out and some solutions and possible improvements in the design of new confined masonry buildings and in the evaluation of existing confined masonry buildings should be proposed. The three series of specimens aspect ratio H / L = 1.15 were scaled and tested to the horizontal cyclic loading at the upper level of the horizontal tie beams. Each of the series was composed of three specimens with a different type of connection between the tie-columns and masonry. One more specimen was built as unreinforced masonry and tested in the same way. Based on experimental results, numerical analysis was carried out, and research was expanded to the other aspect ratio H / L walls and the walls with openings smaller than 1,5m2. The nonlinear seismic response was estimated for one to five stories buildings which have a wall area of 2%, 2.46%, 3%, 4%, 5% and 6% of the gross floor plan under twenty one earthquake a-t diagrams of different design ground acceleration: 0.1g, 0.2 g and 0.3 g. The behaviour factors were evaluated for particular wall types. Allowed interstory drift was determined according to the level of serious damage. The corresponding minimum required densities of the walls in the floor plan of the building were evaluated.