The fundamental objective of the Ocean Seismic Network Pilot Experiment (OSNPE)-which was carried out over a period of about 4 months at a site 225 km southwest of Oahu, Hawaii-was to learn how to make high-quality, broadband seismic measurements in the deep oceans. The OSNPE results demonstrate that broadband data of quality similar to that of quiet land stations can be acquired with seafloor seismographs, but that the location of the seismometer-whether it be on the seafloor, surficially buried within the seabed, or in a deep borehole-has a profound effect on data quality. At long-periods (0.1 Hz), data quality was best for a seismometer deployed 242 m below the seafloor in a borehole. ¿ 2001 American Geophysical Union