The Marine Geology and Geophysics Division of the National Geophysical Data Center (NGDC) handles a broad spectrum of marine geophysical data, including measurements of bathymetry, magnetics, gravity, seismic reflection sub-bottom profiles, and side-scan images acquired by ships throughout the world's oceans. Digital data encompass the first three, while the latter two are mostly in analog form. The marine geophysical data are contained in the GEOphysical DAta System (GEODAS) data management system which now covers both underway trackline marine geophysics (TRKDAS). This data set covers only the TRKDAS subset of GEODAS, which includes 14.5 million nautical miles of cruise trackline coverage contributed by more that 70 organizations worldwide. These digital data are held at NGDC in the MGD77 Exchange Format. The GEODAS/TRKDAS Inventory also tracks 6.5 million nautical miles of analog data from 1484 surveys.