The topography of natural fracture surfaces has a strong influence on the flow and transport properties of fractures. In this paper we investigate the role of anisotropic surface roughness on fluid flow, solute transport, and electrical current flow in fractures. Our results show that the directional characteristics of the surfaces are more important in determining fracture transport properties than is the degree of roughness. Roughness oriented parallel to the primary flow direction substantially enhances fluid and solute transport rates through fractures, with the effect becoming more apparent as the amount of contact area between the surface increases. Roughness oriented transverse to the flow direction inhibits flow rates and delays the movement of solute through the fracture. ¿American Geophysical Union 1991