In this paper, the theory of fuzzy sets, especially fuzzy modeling is discussed to determine elastic modulus of both normal and high-strength concrete. A fuzzy logic algorithm has been devised for estimating elastic modulus from compressive strength of concrete. The main advantage of fuzzy models is their ability to describe knowledge in a descriptive human-like manner in the form of simple rules using linguistic variables only. On the other hand, many parameters will be effected and elastic modulus can be taken into account easily by using the proposed fuzzy model. (c) 2005 Elsevier Ltd. All rights reserved.