Fracture characteristics measured in the Sheeted Dike Complex of the Troodos ophiolite, Cyprus, indicate a decrease in fracture aperture and trace length with depth. Fractures, generally of a contraction-on-cooling origin, tend to be oriented either parallel or perpendicular to the dike margins. High-temperature hydrothermal epidote and quartz fracture fillings are overprinted by late, low-temperature calcite fracture fillings. Paleopermeabilities estimated on the basis of these data using three methods of permeability determination (parallel plate, matrix addition, and a stochastic approach) indicate higher on-axis and slightly lower, late, possibly off-axis, permeabilities than those measured in present-day oceanic crust. ¿ American Geophysical Union 1995