The corrosion of reinforcing steel in concrete structures is a major problem, particularly in industrial and urban environments with high levels of carbon and sulphur oxides, in chloride environments which exist on roads and bridges where de-icing salts are used and in marine locations. Under these conditions reinforcement has to be protected against corrosion. Different types of protection systems have been used in practice, but performance is often unsatisfactory. Stainless steel reinforcing is providing a solution in many situations. Among the different stainless steel grades, duplex steels can allow economical and technical advantages. The purpose of this work is to study the behaviour of reinforced concrete elements in chloride environment and under a temperature range between –27°C and +60°C. Grades N. » 1.4362 and 1.4462 duplex stainless steels have been considered and their behaviour has been compared to that of austenitic stainless steels, grades N. 1.4404, 1.4301 and 1.4306, together with a comparative unalloyed steel. The performance of the above mentioned steels have been investigated under calcium chloride and sodium chloride environments, testing the resistance of the reinforced elements after a testing period simulating, with reference to thermal cyclicity, 30 years of installation. At the same time the corrosion behaviour of the steels has been evaluated by immersion in sodium and calcium chloride solutions, measuring their mass losses as a function of the immersion time.