More reliable assessment procedures of existing RC buildings are currently available, and have been introduced in the Italian and European codes reporting new rules for seismic design and analysis. However, further studies are necessary in order to upgrade such procedures and, specifically, obtain more detailed information on the behaviour of beam-column joints, whose role on the global behaviour of framed RC buildings can be crucial. Until now studies on this issue have been mainly devoted to joint specimens with rigid beams, however joint specimens having flat (flexible) beams are widely used in the European residential RC buildings. To this purpose, given the lack of knowledge, an experimental investigation on full scale beam-column joints with flat beam has been planned and is currently in progress. In the present paper the first results of four tests are reported and discussed.