Vapor-liquid equilibrium data at (26.68, 35, and 55) kPa over the whole concentration range and vapor-liquid equilibria at (23 and 45) kPa over a partial concentration range have been determined for the binary system 1,1,1,2,3,4,4,5,5,5-decafluoropentane (HFC-4310mee) + oxolane (THF), in the temperature range (294 to 322) K. Pure component vapor pressures of each constituent have also been measured in the range of boiling temperatures of the mixture. Depending on the concentration range, the system exhibits positive and negative deviations from ideal behavior. Two azeotropes, rich in oxolane and with opposite deviations, have been found both at (23, 26.68, and 35) kPa, while no azeotrope appears at (45 and 55) kPa. According to these results, polyazeotropic behavior ends in a tangent azeotrope as the pressure increases. The vapor-liquid equilibrium data of the solutions were correlated with the mole fraction by the Redlich-Kister equation.