On the basis of the idea that molecular diffusion occurs by the movement of molecules into voids, a new equation was developed for the determination of infinite-dilution molecular diffusion coefficients in supercritical and high-temperature liquid solvents (T-r greater than or equal to 0.7). An extensive database on diffusion was collected through the literature in order to evaluate the proposed equation and to determine the accuracy of the predictions with no additional parameter adjustment. The predictions were good, with an average absolute deviation of 8.2% for 113 binary systems and 1303 data points. The input data required for the correlations are the solute molecular weight, temperature, and density and the solvent basic properties (molecular weight, critical temperature, and critical volume).