Some early results of a research study on the behaviour of masonry towers under the seismic actions are illustrated. The results regard analysis of the so-called "Tower of Matilde", the bell tower of the Santa Maria e San Genesio Cathedral in the medieval town of San Miniato, near Pisa (Italy). Over the centuries, this tower has undergone numerous consolidation operations and modifications: originally built as a watch tower within the medieval city walls, it was finally incorporated as a bell tower into the Cathedral. Its current layout makes it particularly susceptible to the dynamic actions consequent to the motion of the bells [1] [2] [3], and, probably, to seismic actions as well. Such a hypothesis seems to be to confirmed by the results of these first linear and collapse analyses, performed by considering earthquakes comparable to those actually expected in the seismic area of San Miniato.