SEADATANET aims to develop an efficient distributed Pan-European Marine Data Management Infrastructure for managing these large and diverse data sets. The objective is to network the existing professional data centres of 35 countries, active in data collection, and provide integrated databases of standardized quality on-line. The on-line access to in-situ and remote sensing data, meta-data and products will be provided through a unique portal interconnecting, in the first phase, 11 interoperable node platforms. The development and adoption of common communication standards and adapted technology will ensure the platforms interoperability. This activity will be developed to gradually connect all the other data centres to the interoperable system. The quality, compatibility and coherence of the data issuing from so many sources, will be ensured by adopting standardized methodologies for data checking, by dedicating part of the activities to training and preparation of synthesised regional and global statistical gridded products from the most comprehensive in-situ and remote sensing data sets made available by the participants. These products, easier to interpret by non-specialist users, will be used first to check the data and the system operability, and further to market SEADATANET and to serve a wider range of uses than raw data: e.g. model initialisation, industrial projects and teaching.