The purpose of this study was to prepare a sintered body consisting of monophase cubic spinel type oxide, Mn1.5Co0.95Ni0.55O4, and to evaluate its electrical properties. It was found that cooling from 1400 to 1000 degrees C in nitrogen did not affect the preservation of the sintered rock salt type oxide formed at 1400 degrees C. A crack free sintered body of monophase cubic spinel may be obtained by heat treatment at 1000 degrees C in air, using a specimen cooled from 1400 degrees C at a rate of 500 degrees C min(-1). A heat treatment time in air at 1000 degrees C of more than 48 h was required to convert the rock salt type structure into a perfect cubic spinel structure. The electrical conductivity, sigma, of the sintered cubic spinel oxide synthesized in this work was found to be stable at 100 and 200 degrees C in air and at 100, 200 and 300 degrees C in nitrogen. The sintered spinel oxide was a p-type semiconductor, based on small polaron hopping conduction. The intrinsic hole concentration, n, was estimated to be constant, with a value of 1.6-1.8 x 10(28) m(-3). The mobility, mu, increased exponentially with increasing annealing temperature in both atmospheres, suggesting that the change in sigma is dependent on mu.