Because of increasing waste production and public concerns about the environment, it is desirable to recycle materials from construction and building demolition. This study aimed to find a technique for producing recycled aggregate concrete obtained from construction and building demolition waste. Laboratory trials were conducted to investigate the possibility of using recycled aggregate from different sources in Iraq, as a partial replacement of both coarse and fine natural aggregates or one of them. Recycled aggregate consists of crushed concrete (CC) or acombination of crushed brick (CB) and crushed concrete (CC). The aggregate in concrete was replaced with 10%, 20%, 30% and 50% by weight of crushedconcrete (CC) or crushed brick (CB) and crushed concrete CC. Some of mechanical properties of recycled aggregate concrete as compared to those of conventional normal aggregate concrete are studied. Compressive strength and the splitting tensile strength were determined after curing for 7, 28, and 90 days while density was determined after28 days.From these results, it is reasonable to assume that the use of recycled concrete aggregate does not jeopardize the mechanical properties of concretefor replacement ratios up to 50%. The concrete prepared with the crushed concrete only as a partial replacement of natural aggregate achieved the highest strength values at 7, 28and 90 days. The results suggested that an aggregate that contains 50% recycled aggregate is optimum for producing recycled aggregate concrete The test results showed that the replacement of coarse or fine natural aggregate by recycled brick aggregate at the levels of 10,20,30 and 50% had little effect on the compressive strength of the specimens.