The sintering of particulate composites consisting of a polycrystalline zinc oxide matrix with 10 vol % zirconia inclusions of two different sizes (3 and 14 mu m) was investigated at a constant heating rate of 4 degrees C min-l under an applied stress of approximate to 300 kPa. The presence of the inclusions produced a decrease in both the creep rate and the densification rate but the ratio of the densification to creep rate remained constant during the experiment. The ratio of the densification rate to creep rate for the composites was approximate to 1.5 times greater than that of the unreinforced matrix regardless of inclusion size. The creep viscosity of the composites was higher than that of the unreinforced matrix and increased slightly with decreasing inclusion size.