The critical temperatures, pressures and densities of four perfluoro n-alkanes (perfluoropentane, perfluorohexane, perfluoroheptane and perfluorooctane) have been measured using a sealed ampoule method and a low residence time flow method. Our data have been compared with literature data whenever possible and several inconsistencies in the literature data have been resolved by the present work. Available literature data on the critical properties of all perfluoro n-alkanes have been compiled and trends in the data with chain length of the perfluorocarbon are noted. The performance of several group contribution methods has also been examined and shown to be generally poor for the prediction of critical properties of the homologous series of perfluoroalkanes.