A metal bellows volumometer operating to 250 MPa is described which uses a linear differential transformer in a novel, indirect way to establish the position of the moveable end of the bellows with a precision of about 1 in 60000. Calibration with both water and n-heptane has shown that the effective cross-sectional area of the bellows depends on both pressure and the extent of movement of the bellows. Comparison of excess volumes for acetonitrile-water mixtures calculated from the bellows volumometer data with values determined directly by other authors indicates that the device provides densities accurate to +or-0.02%.