The corrosion of reinforcing steels in concrete is the main reason for the deterioration of bridge decks. An accurate method for measuring corrosion is a fundamental prerequisite for the detection of damaged areas and for planning an effective method for repairing bridge decks. A laboratory study was conducted to estimate the corrosion activity of a reinforcing steel embedded in two types of concrete, ordinary and high-performance, using different corrosion measurement methods. Results indicated that Tafel plot (TP), linear polarization resistance, half-cell potential (HCP), and chloride content methods would assess the same level of corrosion activity in only 24% of specimens.