An advanced computer and communication technology was used to develop an integrated system and software tools for managing a great diversity of oceanographic data collected in the Mediterranean Sea during 1996-2000. Data were obtained during 108 sea cruises, carried out within the framework of the large-scale international research project MATER (mass transfer and ecosystem response), which was financially supported by the Marine Science and Technology (MAST) Programme of the European Union (EU). Data collection involved the active participation of various research vessels and personnel coming from 58 different laboratories of 13 countries. Data formatting as well as automatic and visual data quality controls were implemented using internationally accepted standards and procedures. Various data inventories and meta-data information, accessible through the World Wide Web (WWW), are made available to the user community. A database was developed, which, along with meta-data and other data relevant to the project information, is made available to the user community in the form of a CD-ROM. The database consists of 5861 vertical profiles and 842 time series of basic physical and biogeochemical parameters collected in the seawater column as well as biogeochemical parameters from the analysis of 70 sediment cores. Furthermore, it includes 67 cruise data files of nonstandard additional biological and atmospheric parameters.