This work aimed to develop mathematical models for prediction of the compressive strength of structural concrete (20-70 MPa). The developed models are applicable, also, to mortar and cement paste. They are specified to concrete made with Portland cements conforming to the ASTM C150 (Iraqi Standard No. 5). The available models in literature comprise certain shortcomings that restricted their use to certain conditions. Therefore, the built models were designed to overcome most of these restrictions. The methodology followed in this research work consisted of: a detailed literature survey to define the effective variables involved and the process of modeling. Based on this literature, data were collected, variables were screened and transformed and models were built. Seven models were presented. Six of them were developed by multiple regression analysis and the seventh was built on the basis of dimensional analysis, which is rarely applied to simulate such problems. The models have been tested and validated with raw new data and their prediction were highly significant. An assessment for the models is made and their predictions are compared to some well-known models.