The phase transition temperature of fluorite-type ZrO2-Y2O3 solid solutions containing 8-44 mol% Y2O3 was determined by analyzing the electrical conductance data obtained from sintered samples. In the composition range of 8-17.5 mol% Y2O3, the phase transition temperature (Fss --> Tss + Fss and Fss --> Mss + Fss) could be expressed as follows : t = 5196.9184[ln(ln X)](2) - 12538.894[1n(1n X)] + 7858.1123, where t is the phase transition temperature (degrees C), and X is the Y2O3 content (mol%).