The fluid flow interaction between a two-dimensional rectangular fracture and its surrounding isotropic permeable and homogeneous rock is studied where the surrounding rock is of infinite extent. The interaction is found to depend on two numbers: the aspect ratio of the fracture and the ratio of the fracture permeability and the rock permeability. Furthermore, the interaction is one of two types, one where the fracture is charged and discharged from its sides and another where the charging/discharging takes place through its ends. Approximate solutions that describe these regimes are given. The squared-width fracture permeability is considered, and we show that the interaction of the fracture and the rock is then characterized by a certain aspect ratio. Fractures with aspect ratios smaller than the characteristic aspect ratio are charged/discharged through their short ends, and fractures with aspect ratios larger than the characteristic aspect ratio are charged/discharged through their long sides. A fracture is charged/discharged equally through the short ends and the long sides at characteristic aspect ratio, and the velocity at the center of the fracture is largest for this particular aspect ratio. ¿ American Geophysical Union 1996