Geostatistical filtering (factorial kriging) was applied to the 1981-1996 time lapse seismic data of the TOTAL UK Alwyn field . The goal was to suppress the noises and acquisition artifacts in both data-sets in order to improve the 4D repeatability. After filtering, the measured coherency (both vertically and spatially) between the two equalized cubes was largely improved. Consequently, the 4D events seen in the interval of production appeared to be better focused which permitted to perform a time lapse interpretation with a much higher level of confidence. (France) 3TOTAL E&P UK PLC, Crawpeel road Altens, AB12 3FG Aberdeen (UK)