A process for producing strong alumina ceramics in which needle-shaped .beta.'"-alumina grains are homogeneously distributed in an .alpha.-alumina matrix to provide an increase in bending strength, as compared to the alumina ceramics without .beta.'"-alumina, when fired under similar conditions. The process comprises mixing .alpha.-alumina powder and salts of sodium and magnesium, in a Na:Mg mol ratio of 1:2; wet-mixing and calcining the mixture to form a mixture of (100-5X) mols of Al.sub.2 O.sub.3 +X(Na.sub.2 O+4MgO), wherein X is the number of mols and is not more than 3; forming a dense green body of the calcined mixture and sintering the green body at a temperature and for a time sufficient to form in-situ particles of .beta.'"-alumina distributed in the .alpha.-alumina.