Eighteen core samples from ODP Leg 201 were used to measure vertical permeabilities of subsurface sediments from the equatorial Pacific and the Peru margin. Measured permeabilities ranged over three orders of magnitude from 10–18 m2 to 10–16 m2. The repeatability of measurements indicates that the error in the laboratory methods is small compared to the variation among sediment types. The lower permeabilities represent lithified oozes and clay-rich sediments, whereas the higher permeabilities represent unlithified oozes and silt-rich sediments. The rate of decrease in permeability with increasing effective stress varied among samples.