This thesis presents results of research, performed within a larger scientific project, concerning reinforced concrete frames filled in with masonry. Currently available regulations do not, in most cases, take into account masonry infill as a factor in structural analysis design; if they do, however, the design is extremely complex. Scientific research has so far indisputably confirmed the fact that masonry infill affects the structural behaviour of reinforced concrete frames. This is primarily visible in frames' transverse load carrying capacity and stiffness. The thesis displays experimental research of reinforced concrete frames additionally filled in with masonry. The reinforced concrete frame model has been designed based on a prototype that is a rectangular reinforced concrete frame structure with floor plan dimensions 17x16 meters and the height of first floor 3,75 meters, with upper six floors 3 meters high. The prototype model was designed according to current regulations (EC2, EC8), made out of C30/37 concrete and B500B reinforcement. According to such a prototype, a real life model of a one-story, one-span reinforced concrete frame was constructed in scale of 1:2,5, following all the scaling rules. Based on experimental testing of masonry elements, masonry infill specimens and mortar (glue) used to build the infill, their main mechanical features were obtained and subsequently used to distribute the masonry infill into three categories; high strength infill (using brick blocks MO10), medium strength infill (using brick blocks MO5) and low strength soft infill (using aerated autoclaved concrete blocks MO2.5). The division of infills was designed aiming to find out the effect of masonry elements' (masonry infills') strength on the behaviour of reinforced concrete frames with masonry infill. Ten models were tested applying constant vertical load on columns and cyclical static horizontal load. Three models were tested for each type of masonry infill as well as one model of a reinforced concrete frame with no infill. Main mechanical features of concrete and reinforcement used to build the models were also tested. Obtained experimental results for these models of reinforced concrete frames with masonry infills were elaborated in detail concerning the infill collapse mechanism, lateral load carrying capacity, lateral stiffness, hysteretic energy (energy dissipation, energy absorption and attenuation coefficient) and categorization of damage to masonry infill. Analytical results, obtained based on existing models and structural analysis procedures of reinforced concrete frames with masonry infill, were compared with experimental results. Numerical results were obtained by applying a numerical macro model that was used to design the masonry infill (non elastic panel element). Input data necessary for this model's structural analysis were defined by harmonization of experimental models' data. Numerical results were used for impact analysis of input parameters on transverse load carrying capacity, transverse stiffness, hysteretic energy and forces in the diagonals of the masonry infill within a reinforced concrete frame with masonry infill. Additional analysis was performed on a calibrated model. Following parameters were observed: reinforced concrete frame geometry; compression diagonal geometry; diagonal strength (of the masonry infill); vertical load in the columns; quantity of reinforcement in the columns; cross-section of the columns; number of fields and methods of horizontal load application. A method of linear structural analysis for reinforced concrete frames was proposed with the aim to apply its results in everyday engineering practice. This method analyzes the reinforced concrete frame with masonry infill as a system („frame+wall“) and it is used for the system's dimensioning. The behavior of such structural systems’ models under earthquake action was controlled performing the N2 method, namely, by determining target displacement in the nonlinear static field.