The paper presents a state-of-the-art review of the current understanding of the seismic behaviour of tunnels. Emphasis is placed on recorded responses of actual tunnels during past earthquakes, as well as relevant experimental studies. In particular, the observed seismic performance of tunnels is initially discussed, by providing cases of reported damage during past earthquakes. This is followed by a review of the current monitoring systems for this infrastructure, which can be used to create future case studies based on actual recordings of the seismic response. Subsequently, the paper provides a summary of relevant experimental studies that took place in the centrifuge or on shaking tables, followed by a short discussion of current analy...