An apparatus was constructed for the measurement of critical parameters and vapor pressure at high temperatures. Its reliability was confirmed with two commercially available chlorofluorocarbons, HFC-134a (CF3CH2F) and HCFC-142b (CH3CClF2). Measured overall values fell well within the range of other reports. Attempts were made to measure the critical parameters of 21 newly synthesized hydrofluoroethers, that are potentially useful for dry-cleaning and have critical temperatures higher than 450 K. Before the measurements, great care was taken to remove traces of moisture from the samples. Among these new compounds, six were thermally unstable and four were rather unstable even after dehydration. The critical parameters of the remaining 11 were successfully obtained with good reproducibility. Their Antoine and Wagner parameters were also reported.