A great number of Italian highway bridges have been provided with seismic isolating devices. As a typical 
example of the criteria for the design of such structures the bridges of a new highway are illustrated. They are composed of various continuous multi-span sections. The seismic isolating systems have been designed on the basis of the dissipating behaviour of elastic-plastic restrainers. With reference to the cases studied, general considerations concerning the design of optimum structural configuration suggested by the use of seismic isolation, are also discussed.