MTPII-MATER 1996-1999 (Mass Transfer and Ecosystem Response) project database includes information and data collected during the largest regional integrated project of the European MAST 3 (Marine Science and Technology) framework programme. The 108 project sea cruises (about 1,000 days of work at sea), 3,700 stations, 130 time series, as well as the equipment used are described. All the multidisciplinary data collected and validated by some fifty laboratories are available in a unique Medatlas format. This high-quality database is a major tool for present and future scientific and technical programmes in the Mediterranean. Thanks to extraction and display software tools included in the CD-Rom, the database can also be used by non-specialists, teachers and students.