The Mediterranean Oceanic Data Base (MODB) provides data products, analysis software packages, and visualization tools to scientists working in the Mediterranean Sea. Available data sets include over 100 000 historical profiles of temperature and salinity collected in the Mediterranean, Black and Azov Seas between 1900 and 1993. In addition, temperature, salinity, u-component current velocity, and v-component current velocity fields are available for winter, spring, summer and autumn on a 1/4-degree grid and 19 levels on the vertical, objectively reconstructed using a variational analysis scheme. The velocity fields are diagnosed from the seasonal climatology using a free-surface primitive equation model. Mediterranean bathymetry is also available from the ETOPO5 data base, global depths and elevations on a 5-minute grid. Online extraction software allows for subsetting of the bathymetric data. Software products include the variational analysis package, with a user interface, which was used to reconstruct the gridded fields; Ocean Data View PC-software for MS-DOS to visualize hydrographic profiles and sections; and ModbWin, a visualization program for the gridded data under MS-Windows. Also available are several technical notes, scientific publications describing the products, an atlas report that includes figures illustrating the seasonal climatology of the Mediterranean, and various images in gif or jpeg format representing subjects related to the Mediterranean Sea.