ABSTRACT: Object of the research activities reported within this paper is one of the best-preserved and famous roman structures of Padova: San Lorenzo bridge. It was built between 47 and 30 BC on the river Medoacus (the old flow of the Brenta river) and over its long history it was gradually incorporated into medieval and modern structures. Thanks to the archaeological excavations carried out in 1938 it was totally rediscovered and currently it is located below the modern roadway. In July 2013, after the survey of some detachments of stone from the intrados of the arch bridge, the municipality gave the task to the University of Padova to carry out an investigation campaign to study its health state. Aim of this work was to define the structural conditions of the bridge, control its degradation state and define possible actions to be implemented.