Hollow concrete blocks are one of the most extensively used wall construction material inrnmajor cities of our country, Ethiopia. Aggregates, cement, and water are the main materialsrnrequired for the production of this building material. To achieve the required physicalrnstrength and dimensions of requirements and standards, they are manufactured fromrnconcrete and processed into molds. While comparing with others, HCB masonry isrnbelieved to be cost and time efficient and economical solution in construction. rnThe production of cement is one of the environmentally unfriendly processes due to thernrelease of COrn2rn gas to the atmosphere. In addition to its negative environmental impactrncement is also one of the most expensive materials when compared to the otherrnconstituents of the HCB. On the other hand, marble processing factories have a problemrnof disposing of the waste marble powder. Using marble waste powder in HCB production,rnthe effects of partial replacement of cement with marble waste powder on the performancernof HCB was investigated. The physical properties and compressive strength of 288 HCBsrnwere determined. rnThe laboratory-based investigation for the partial replacement of cement with marblernpowder in HCB production was conducted. Tests on the suitability of materials used andrntheir performance in terms of known engineering properties were carried out. The focusrnwas the partial replacement of cement with marble powder in the order of, 0%(Control),rn10%, 20%, and 30% of cement by weight for Class A, B and C HCBs of size 20x20x40cm. rnReplacement at 10%, 20%, and 30% ranges result in compressive strength reduction thanrnthat of 100% cement. However, the compressive strength of blended cement with 10% torn30% replacement ranges satisfy the minimum compressive strength set by Ethiopianrnstandard of HCB for class A, B and C. Other properties of marble waste blended cementrnof HCBs such as density and water absorption remain within the acceptable limits ofrnEthiopian standard. Therefore, further investigation should be made for more percentagernof marble waste replacement.