In recent times, many researchers are attempting to predict the elastic properties of concrete by using previous work or composite models. In this study, it is aimed to apply composite material models to estimate the modulus of elasticity of slag concrete. The compressive strengths of wet cured slag concrete with different slag content and water to cement (w/c) ratios, are used in the calculation of the modulus of elasticity by using methods developed by previous works. The previous work model estimations are firstly assumed as the reference values of modulus of elasticity of slag concrete. Then, modulus of elasticity is also estimated by using composite models and compared to the reference modulus of elasticity. It is observed that composite models can also be employed to estimate the modulus of elasticity for slag concrete, using the assumptions of the moduli of elasticity cement and aggregate phases given in this study, where only the compressive strengths are determined by experimental tests. (C) 2009 Elsevier Ltd. All rights reserved.