The Water activity R&D project, carried out in cooperation with ONF and Vilmorin, aimed to demonstrate the effectiveness of Water Activity assessment applied to forest seeds and pollen moisture management as a replacement for moisture content assessment. Water Activity assessment is a quick and non destructive technique to qualify the kind and the chemical potential of water remaining in the sample. The growth of micro-organisms require a specific osmotic pressure, or Water Activity(Aw), between cell walls and medium. The reactivity and depreciating ability of hydrolytic reactions, enzymes activity, lipid oxidation or biotic agents growth are dependent on Aw rather than on MC. Consequently, seeds and pollen preservation implies Water Activity control instead of moisture content check. Water dynamics in seeds and pollen have been described by the mean of sorption isotherms, this demonstrates clearly the variability of forest materials and consequently the poor reliability of moisture content for successful moisture management. As a conclusion, Water Activity assessment appears to be a reliable and a quick method to evaluate the ability of a given sample to be stored successfully. This technique has been transferred and is now regularly being used by Vilmorin and ONF for forest seeds and pollen moisture management.