Apparatus for the measurement of PVT properties and bubble points of petroleum reservoir fluids is described. The limits of operation are 700 bar and 100-degrees-C. An appraisal has been made of the sources of error in the measurements. The equipment has been tested with pure CO2 at a series of temperatures and the results have been shown to be in good agreement with the IUPAC equation of state, the average absolute deviation of 53 density data points being 0.11%. PVT data have been obtained for a separator crude oil from a British field at temperatures in the range 20.6-degrees-C to 65.6-degrees-C, and for its mixtures with CO2 at 65.6-degrees-C. The phase behaviour of the system has been discussed in the light of related literature data. Bubble points and isothermal compressibilities have been measured and tabulated.