The variation of compressive and flexural strengths of ordinary and high-performance micro-concrete at high temperatures was examined. Compressive and flexural strengths of ordinary and high-performance micro-concrete which were exposed to high temperatures (200, 400, 600, 800 and 1000 degrees C) and cooled differently (in air and water) were obtained. Compressive and flexural strengths of these concrete samples were compared with each other and then compared with the samples which had not been heated. On the other hand, strength loss curves of these concrete samples were compared with the strength loss curves given in the codes. Experimental results indicate that concrete strength decreases with increasing temperature, and the decrease in the strength of ordinary concrete is more than that in high-performance concrete. The type of cooling affects the residual compressive and flexural strength, the effect being more pronounced as the temperature increases. Strength loss curves obtained from this study agree with strength loss curves given in the Finnish Code. (C) 2006 Elsevier Ltd. All rights reserved.