In this paper we calculate the contribution D s to the self-diffusion coefficient D 0 from the coupling of solute motion to solvent density fluctuations in an infinitely dilute near-critical binary mixture using the methods of fully renormalized kinetic theory in the disconnected approximation. The expression for D s is found to be similar to mode-coupling expressions for diffusion coefficients in dense or supercooled liquids. As a function of the solvent density , and along the critical

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... m, D 0 exhibits an anomalous decrease in the vicinity of the critical point that originates in the vanishing of D s according to the scaling relation D s ϳ(Ϫ c ) 2 , where c is the critical density. An analogous decrease in D 0 has recently been observed in the simulations of Drozdov and Tucker ͓J. Chem. Phys. 114, 4912 ͑2001͔͒ on a neat liquid of Lennard-Jones particles, and has been ascribed to local density inhomogeneities in the medium.