The effects of infill panels on the response of r.c. frames subjected to seismic action are widely recognised and numerous experimental investigations as well as several analytical models have been developed on this subject. In this work, referring to specific materials and structures commonly used in Europe, experimental tests performed on bricks, mortar, single and double infill walls and finally on bare and infilled r.c. portals are described and discussed. Together with the experimental activity, the implementation of simple non linear models for masonry panels of infilled frames are described. The accuracy of a numerical model has been assessed through comparison with experimental results obtained form cyclic tests on r.c. frame specimens. The numerical model has been applied on multy-storey r.c. frames with different infill configurations. This work won the 7th edition of the "Brunello Sarno" prize.