Experiments in sandpacks and Berea sandstone were performed to measure dispersion and steady-state relative permeabilities. Phase behavior, interfacial tension, and viscosity determinations were made using DS-10 and TRS 10-410 surfactants to formulate a suitable three-phase micellar mixture. Relative permeability measurements were made at steady-state on both high tension brine-oil pairs and a low tension three-phase brine-oil-surfactant-alcohol mixture followed by injection of radioactive and chemical tracer(s) to investigate dispersion. The classical solution to the convection-diffusion equation for single-phase flow is generalized to multiphase flow, allowing interpretation of the multiphase flow experiments. Dispersivity was a strong function of phase, phase saturation, porous medium, and inter-facial tension. Dispersivity values varied over two orders of magnitude. Extremely early breakthrough of carbon-14 tracer in the high tension oil phases was an unexpected result. Tritium tracer breakthrough curves, however, were similar to 100% saturation breakthrough curves (except for a shift due to the oil saturation). Unlike the aqueous and oleic phases, the microemulsion phase dispersivity was not a function of saturation. Three-phase experiments indicated that the aqueous or oleic phase relative permeability is a function of its own saturation only. During three-phase flow, a change in wettability from the original water-wet state occurred.