Recently, there have been many reported cases of early re-deterioration occurring in partially-repaired con crete structures. In order to clarify the mechanism causing this phenomenon, the deterioration of reinforced concrete speci mens under salt attack was simulated and then remedial maintenance operations such as section restoration and surface coating was performed. After maintenance, the specimens were then exposed to both inland and marine conditions, and various experiments and measurements were conducted to clarify the mechanism of re-deterioration. This paper reports the results from 5 year, continually exposed specimens as part of a collaborative research project.