The results and reverse Monte Carlo analysis of diffraction measurements of BF3 in the liquid and supercritical state are presented. Liquid BF3 displays order only in the first coordination sphere around the average molecule and there is no intermediate range order. Liquid BF3 is thus not a layered liquid. Angular analysis using reverse Monte Carlo modeling shows that the dominant structural motif in the solid state, that of pseudo trigonal bipyramidal [3+2] coordination at B is partially retained in both the liquid and supercritical phase, though in the latter, this structural preference is greatly reduced. The structure of the supercritical phase retains the same intermolecular contact as the liquid phase, though the structural sites and population of these sites is much more widely distributed. (C) 2003 American Institute of Physics.