Magnetic resonance (MR) imaging was used to observe the flow of dense (FC-75) and light (dodecane) non-aqueous phase liquids (NAPLs) through a water saturated dolomite fracture. Dynamic two-phase behavior was influenced by (1) buoyancy of the NAPL relative to the aqueous phase, (2) fracture aperture distribution, and (3) alteration of wettability by long-term presence of NAPL phase. MR imaging was capable of characterizing the fracture geometry and the fluid flow, but was limited by outlet flow conditions in the sample and acquisition times. This method permits observation of two-phase flow under natural wettability and matrix porosity, providing significant advantages over plastic or glass replicas.