A simple modification of a high resolution N.M.R. spectrometer is presented, permitting determination of self-diffusion coefficients at pressures up to 200 MPa in the temperature range between 140 K and 450 K. The self-diffusion coefficients of CHF3 are determined between 142 K and 250 K. The activation energies derived from the data are [EaD]p = const = (6·1 ± 0·4) kJ mol-1, [EaD]V = const = (3·5 ± 0·4) kJ mol-1. Except for the lowest temperatures, compressed CHF3 appears to behave as a normal, rough hard-sphere fluid.