Some solute-solvent systems show vanishing or negative dynamic intrinsic viscosity [η]ω at any frequency ω. For consistency with this observation the conventional model of dilute polymer dynamics is modified to account for the gradient of solvent velocity in the vicinity of a polymer bead. With simplifications which are strictly valid only for polymers of low molecular weight M or for large ω, [η]ω is changed only by the addition of a term [η]γ. In units of ml/g [η]γ is independent of M and ω and may be positive or negative. The same type of theory is applied to the effect of polymer on the translational and rotational friction constants of small solute molecules A, e.g., labeled solvent. With reasonable estimates of a distance of closest approach between polymer beads and molecules A, the friction constants of A increase with polymer concentration at roughly the same rate as the viscosity of an oligomer solution of the same polymer species. A molecular theory of the coupling constant between a polymer bead and a solvent velocity gradient is not essential, but a few possibilities are considered. The coupling constant may reflect modifications of the solvent by the polymer, as has been suggested by others, or differences in the deformability of oligomers and solvent, etc. The deformability argument seems to necessitate friction matrices with negative eigenvalues, and a reconciliation of such behavior with stability requirements is presented. © 1990 American Institute of Physics.