(ThxCe1-x)O-2 microspheres (x = 0.50, 0.75, and 0.95) prepared by sol-gel microsphere technique were compacted to pellets. The sintering kinetics, diffusion mechanism, and activation energy of the (ThxCe1-x)O-2 pellets were investigated by dilatometry for 1100 degrees C, 1200 degrees C, and 1300 degrees C. The rate controlling sintering method, one of the most sensitive methods, was chosen to investigate the sintering kinetics. The pellets were heated with a rate of 10 degrees C/min and were held for 10 h at the above mentioned temperatures under isothermal conditions. The activation energies for the (Th0.50Ce0.50)O-2, (Th0.75Ce0.25)O-2, and (Th0.95Ce0.05)O-2 pellets were calculated as 305, 315, and 419 kJ center dot mol(-1), respectively. In the experiments, green densities of the mixed-oxide pellets were determined as 45% to 47% of the theoretical density for all of the studied ratios. Sintering densities reached up to 94% of theoretical density after sintering at 1300 degrees C. Scanning electron microscopy images of the pellets were taken.