A study was made in one of the cement factories in Dar es Salaam, Tanzania, where Ordinary Portland Ce-ment (CEM I 42.5N) and Portland limestone cement (PLC) (CEM II/A-L/32.5R) are produced and conform-ing to the Tanzania Standard TZS 727 (Part1): 2002, which is equivalent to EN 197 published by the com-mittee for European normalization (CEN). A comparison was made between the two types of cements in terms of physical, chemical and mechanical properties. It was found out that they all complied with the standards, that there was no significant difference in their setting times and that the Portland cement had higher strengths than the PLC. Also it was observed that there was a slightly lower water demand for the same consistency when compared to OPC and hence there is an improvement of the cohesiveness of a con-crete mix when PLC is used. It was concluded, however, that the two cements are different and that using the two cements interchangeably as is done in Tanzania is wrong because they do not have equivalent strengths and therefore equivalent performance since the PLC is not optimized.