In this thesis, tensile tests and pitting corrosion tests are done on carbon steel and AISI 316 austenitic stainless steel after thermal aging in different temperature range and time intervals. Between 600ºC and 900ºC, the strengths of AISI 316 show monotonic decrease. This decrease is caused by the more significant grain growth and reduction of dislocations as the temperature goes up. At a fixed temperature in this temperature regime and for up to 7 days, however, AISI 316 does not show any change in its tensile behavior. It may thus be said that the ability to reinforce concrete is not affected at a fixed annealing temperature for up to 7 days. Between 600ºC and 900ºC and for annealing time less than 10 hours, a higher temperature would lead to more softening of carbon steel compared with AISI 316. After 1 day, however, the softening of carbon steel annealed at 700ºC is more serious than annealed at 800ºC. Because a fire accident is unlikely to be longer than 10 hours, it may be said that a higher fire attack temperature is more damaging to carbon steel rebars. At both 600ºC and 800ºC, the tensile behavior of carbon steel does not change too much. At 700ºC, however, carbon steel shows gradual softening, because the carbides will spheroidize. Under 500ºC, both AISI 316 and low-carbon steel do not show much difference even after annealing for 7 days at a particular temperature. It means both materials are not much affected by a low-temperature fire attack. For the pitting corrosion behavior in all the three solutions (3.5% NaCl, saturated Ca(OH)2 and a combination of both), the polarization curves for 1 hour annealing and 7 days annealing are all nearly coincided, for both carbon steel and AISI 316. Therefore, the pitting resistance of both AISI 316 and low-carbon steel would not be compromised too much even after a fire attack under 900ºC.