The MEDATLAS hydrological data base, has been created by a consortium of several data centers, including HNODC (Greece), IEO (Spain), EPSHOM/CMO (French navy), IFREMERJSISMER the coordinating center (France) and ICES (Denmark) as the supervisor of the quality control procedure, in the frame of the MEDATLAS project. This project is a MAST supporting initiative for ocean data and information management. Its objectives were to assemble a comprehensive data base of temperature and salinity profiles collected in the Mediterranean sea by t he scientific laboratories and the navies, to check them for quality and to revise the climatological statistics by using this updated date set. An important part of the work has been devoted to define a common protocol to archive the data sets and to ensure a coherent level of quality for the data which originate for various sources within the consortium and from other data centers : ICES, World Data Center A, MODB, BODC, DOD. The common protocol includes: - an exchange forma t (the MEDATLASIMODB format) - a quality control procedure. Both are based on t he UNESCO/IOC and MAST recommendations. This paper describes The MEDATLAS/MODB format, the common quality checks protocol and the hydrological data sets gathered in the frame of the MEDATLAS project.