Abstract: Process for producing sintered aluminum nitride bodies, comprising sintering a relatively impure aluminum nitride powder comprising at least 95% by weight aluminum nitride and having no more than 3% bound oxygen content, no more than 0.6% metal or metal compound impurities, and no more than 0.5% silicon or carbon impurities, the sintering being carried out by heating the aluminum nitride body from room temperature to the sintering temperature at a rate of no more than 250.degree. C. per hour; introducing an inert gas containing from 1 to 4% by volume hydrogen until the temperature reaches 1200.degree. C.; continuing to introduce solely an inert gas as the temperature is further increased to the sintering temperature; sintering the body at a sintering temperature of from 1600.degree. to 1900.degree. C.; and cooling the sintered body at a rate of no more than 300.degree. C. per hour.