This article outlines the methodological guidelines that will be applied in the framework of the program Agri-BALYSE in order to compile life cycle inventories for about 110 French agricultural products. Special emphasis will be given on the treatment and the capture of the four main sources of variability for agricultural production systems: Variability due to differing natural production conditions, variability due to different production methods, variability due to different agricultural practices within a given production method and variability due to uncertainty of measurements. The guidelines are compiled in the Agri- BALYSE data collection guide which will be available end of summer 2011. Given the strategic importance of the Agri-BALYSE database, the data collection guide may become a national standard for LCA of agricultural products in France.