The binary mutual diffusion coefficient (D) for a dilute solution of a self-associating solute and the solute intradiffusion coefficient (D*) are related by D = D* + (dD*/dC), where C is the total solute concentration. This relation is extended to multicomponent systems. For solutions of two associating solutes, the ternary mutual diffusion coefficients D₁₁, D₁₂, D₂₁, D₂₂ and the solute intradiffusion coefficients D^*₁, D^*₂ are found to be related by D₁₁ = D₁* + C₁∂D^*₁/∂C₁, D₁₂ = C₁∂D^*₁/∂C₂, D₂₁ = C₂∂D^*₂/∂C₁, and D₂₂ = D₂* + C₂∂D^*₂/∂C₂. These results are used to interpret coupled diffusion in water + AOT (sodium bis(2-ethylhexyl)sulfosuccinate) + n-heptane (water-in-oil) microemulsions. Although the water(1) and AOT(2) components associate and intradiffuse together through the heptane–continuous solvent as AOT-coated water droplets, and hence D^*₁ ≈ D^*₂, the mutual diffusion of AOT is more rapid than that of water (D₂₂ > D₁₁), and there are counter-current coupled flows of AOT (D₂₁ < 0) and large co-current coupled flows of water (D₁₂ > 0). This behavior can be understood by noting that added water reduces the Brownian motion of the droplets by swelling the water cores (∂D^*_i/∂C₁ < 0), whereas added AOT reduces the droplet size (∂D^*_i/∂C₂ > 0) by providing more surfactant to coat the water. The predicted water and AOT intradiffusion coefficients are the eigenvalues of the mutual diffusion coefficient matrix.