The properties of six locally manufactured ordinary Portland cements supplied from different sources were evaluated, through chemical, physical and mechanical testing. The cements delivered fulfil the requirements of the ESS373/91 for ordinary Portland cement and comply with type II Portland cement as classified in the ASTM C 150. The tested samples show some variations in the measured characteristics in terms of their chemical, phase composition, setting times, fineness and compressive strength. By changing the source of the cement, the properties of the fresh and hardened concrete are strongly affected. At a fixed water/cement ratio the workability of concrete markedly varies, and in order to attain a fixed value for workability, the water demand changes drastically. These behaviors could be attributed to the fineness and the phase composition of the cement. Keywords: Portland cement, phase composition, concrete, workability and gain of strength.