A special aluminum nitride (AlN)-glassy carbon artificial dielectric ceramic for microwave absorption at low temperature has been developed at the Continuous Electron Beam Accelerator Facility to manufacture the higher order mode (HOM) loads used in the superconducting cavities of the machine. As the HOM loads share the same ultrahigh vacuum as the superconducting cavities, very tight vacuum requirements are imposed on the HOM load’s material. Vacuum outgassing rates have been measured and compared for AlN-15% glassy carbon artificial ceramic in fully degassed condition produced by heating to high temperature in a vacuum furnace. In addition, the effect of exposure to air, nitrogen gas, and isopropanol is discussed. A typical outgassing rate at room temperature is 2.5 X 10(-11) Torr l/s/cm2, 24 h after initial pump down. Baking 24 h at 150-degrees-C was sufficient to attain an outgassing rate of less than 4 X 10(-12) Torr l/s/cm 2. However, when the ceramic has a lower bulk density or a higher apparent porosity, the outgassing rates can be two orders of magnitude higher.