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BIPM holds every four year the ICAG (International Comparison of Absolute Gravimeters) which is always accompanied by a relative gravity campaign (Becker and Groten 1983，Jiang et al. 2005). It gives high precision relative gravity ties and vertical gradients measured over the BIPM ICAG-network. For the 7th ICAG in 2005 it includes sites with a gravity difference up to 9 mGal*. 12 institutes of 10 countries with 15 gravimeters of 6 different types were employed. This paper reviews the organisation of the relative campaign，the raw data analysis，the relativeonly measurement adjustment and the combined adjustment of the relative and absolute data. Related problems issued during the measurements and data processing is introduced.The Absolute determination uncertainty and the relative raw data analysis，the comparison between the relative-only adjustment，the absolute-only adjustment and the combined adjustment show that the uncertainty of an adjusted gravity difference given by the relative campaign is of the order of 1-2 μGal，probably +1.3 μGal，and that of the gradient is of the order of 1-2 μGal/m. The uncertainty of the adjusted absolute gravity value is about 2 to 3 μGal.