A mode-coupling treatment of nonpolar solvation dynamics in supercritical fluids is presented. Both neat fluids and dilute attractive supercritical solutions are considered. The equilibrium solvation time correlation function for the solute fluctuating transition frequency is obtained from the mode-coupling theory method and from molecular dynamics simulations. Theory is shown to be in good agreement with simulation for all solvent thermodynamic conditions studied. The microscopic origins of the density dependence of the time correlation function are discussed. (C) 2003 American Institute of Physics.