The effects of alkyl chain length of homologous alkyl sulfate surfactants ranging from C-8 to C-14 on the diffusion behavior of both the surfactant and gelatin have been investigated by pulsed-gradient spin-echo NMR spectroscopy. Changes in the diffusivity of the surfactant can be rationalized in terms of a two-state model consisting of gelatin-bound micelles in equilibrium with freely diffusing unimeric surfactant. A minimum in the diffusivity of gelatin is observed when the binding of surfactant amounts to about 1 micelle/strand. The depth of of this minimum increases with the chain length of the surfactant. These effects are explained in terms of micelle-mediated transient cross-links as proposed by Greener et al. (Macromolecules 1987, 20, 2490). The effective strength of the cross-links is a decreasing function of the number of micelles/strand because of the electrostatic repulsion between the micelles; the strength increases with an increase in the size of the micelles.