Special waste incinerator ashes (fly and bottom) and steelmaking slag were attrition milled, separately or in blend to give powders that were pressed into specimens. Pressed samples were sintered in a muffle furnace to form monolithic ceramics that were characterized by density, shrinkage on firing, water absorption, bending strength, hardness and fracture toughness measurements. Crystal phases were investigated by XRD and microstructures were observed by SEM. Excluding materials prepared using fly ashes alone, the mechanical properties of the sintered specimens are fairly good thank to their fine microstructure. They contain equiaxial grains and a limited amount of vitreous phase. Shrinkage on firing is high for every composition and the residual porosity seems to be mainly on the surface since water absorption is low. Samples obtained by the various blends were aged in an acid (HCl) water solution to evaluate the elution of the components. Leaching test data show that the sintering procedure limits the release of most of heavy metals present in the staning waste.