Prealloyed copper powder containing 2.5wt. %Al was processed in a planetary ball mill to evaluate matrix hardening due to formation of Al2O3 particles in situ by internal oxidation. After milling, the powders were heat treated in hydrogen in order to reduce copper oxide formed on particle surfaces during milling. The compacts were made by hot pressing. The examinations show that the compacts possess a good combination of high strength and high electrical conductivities. After 5h of milling the microhardness of the prealloyed compact was 3 to 4 times higher than that of the as-received electrolytic copper compacted under the same conditions, while the conductivity was 68% IACS. Also, it was found that the prealloyed compacts preserved much of the hardness after exposure to high temperature in inert atmospheres.