The excess enthalpies HE of mixing of hexafluorobenzene with each of the donors pyridine, 2,6-dimethyl pyridine, 2,4,6-trimethyl pyridine, triethylamine, N,N-dimethyl aniline (DMA), and the o-, m- and p-N,N-dimethyl toluidines (o-, m- and p-DMT) have been measured as a function of composition and, where possible, at 25, 50 and 70°C. DMA and m- and p-DMT give solid complexes with hexafluorobenzene, thus preventing measurements at 25°C. The large exothermic heats, and the positive excess heat capacities, CEp, obtained with the majority of systems, indicate the presence of strong complexes in solution.