This state-of-the-art report is intended to cover known practice and research relating to corrosion in prestressed concrete systems. ACI 222R covers factors that govern corrosion of steel in concrete@ measures for protecting embedded metals in new construction@ techniques for detecting corrosion in structures in service@ and remedial procedures. In general@ ACI 222R focuses on the mechanisms that relate to the corrosion of nonprestressed steel. Many of the mechanisms discussed in ACI 222R are valid for and apply to prestressing steels in concrete. This document supplements ACI 222R by presenting information concerning mechanisms that affect prestressing steels in concrete. It includes basic coverage of the metallurgy of the various commonly used prestressing steels as necessary background information to understand the mechanisms of deterioration of prestressing steels. Techniques@ both current and proposed@ for evaluation of prestressed structures with respect to corrosion of strands and tendons are also reviewed. A history of field performance@ covering documented cases of corrosion-induced failures in prestressed concrete members@ is included in this report. Finally@ this document describes methods of protection as well as remedial techniques that can be applied to existing structures with corrosion.