In this study, the alterations at the reinforcement steels embedded in corroded and not corroded reinforcement mortar specimens after high temperatures were investigated. These reinforced mortar specimens with 3 cm and 5 cm covers were first exposed to 20, 100, 200, 300, 500 and 800 degrees C temperatures. Subsequently, to determine the mechanical properties tensile tests were applied on the steels taken out of these mortar specimens. With the tensile tests performed stress-strain curves of the steel bars exposed to several temperatures were obtained. Besides, yield and ultimate strengths of the steel bars were also determined. It is obtained that, high temperatures affected the mechanical properties of reinforcement steel considerably negatively. Results of the study have shown that the larger the covers are the better the steel bars are protected against high temperatures. (C) 2010 Elsevier Ltd. All rights reserved.