A detailed comparison of the properties and microstructures of conventionally sintered and microwave sintered samples of 3 mol% and 8 mol% yttria zirconia was performed. Identical thermal profiles were used for both types of heating. For both materials, microwave heating was found to enhance the densification processes which occur during constant rate heating. The 3 mol% yttria zirconia material exhibited a shift in the grain size/density relationship which favours densification, resulting in higher density samples with smaller grain sizes at densities below 96% of theoretical density. At higher densities, significant grain growth occurs. For the 8 mol% yttria zirconia material, the grain size / density relationship remained unchanged. Differences in the response of the two materials are attributed to the differences in the activation energy for grain growth, and in grain boundary mobility. Modulus of rupture and toughness of both microwave and conventionally sintered samples were similar. Following isothermal heating at 13000C, microwave heated samples were found to be significantly more dense than conventionally heated samples. This temperature also restricted grain growth once densification was approaching completion. These findings have significant implications for the commercial application of microwave sintering. It appears that this method of sintering produces a superior product to conventional sintering.