The relationship between apparent diffusion coefficients, D', of electroactive probe and the microstructure of an oil-in-water anionic microemulsion, sodium dodecyl sulfate (SDS)/dodecane/1-pentanol/0.1M NaClaq has been investigated. Three probes, ferrocene (Fc), Fe(CN)(6)(3-) and methyl viologen (MV(2+)) allowed the effect of different microstructure and interactions on the D'-values to be investigated. The results indicate that the droplet as well as bicontinuous microemulsion structures can be identified and point to the effects of cross-phase exchange, partitioning, and multiple binding on the D'-values.