A Taylor dispersion apparatus was designed and constructed for measuring diffusion coefficients in supercritical carbon dioxide. The limiting mutual diffusion coefficients of naphthalene, phenanthrene, and hexachlorobenzene were measured in the temperature range of 308-328 K and at pressures between 96.4 and 249 bar. The triple point volume for carbon dioxide extrapolated from the data closely matches its literature value. In addition, a simple correlation based on hard sphere theories was developed for prediction of diffusivities of heavy molecular weight organics in supercritical carbon dioxide.