The purpose of this mission, which received financial support from the French Embassy in Bangkok (contract MAE 428015), was two-fold: - Make contact with the partners: the Rubber Research Institute of Thailand (RRIT) and Kasetsart University (KU, Bangkok), with a view to my future assignment (July 2001) in Thailand in connection with the DORAS-Rubber Ecophysiology project; - Take part in the first set of excavations of rubber trees subjected to different tapping levels, to estimate relations between biomass growth and tapping intensity (CRRC site). This operation contributes to the research programme being implemented by Miss Unakorn Silpi for her thesis (PhD), which is one of the two axes of the ecophysiology componenet of the DORAS-Rubber project. All the desired contacts were made, at both KU and RRIT-DOA. An official letter of agreement for my assignment at Kasetsart University was received on 19th March. The uprooting operation took place under excellent conditions, thanks to the availability of all the equipment and personnel required. In compliance with the protocols, 12 trees (4 treatments x 3 clones) were uprooted and an analysis of biomass distribution by stratum and by compartment (leaves, trunk, branches, roots) was carried out at the same time as a description of the architecture. Prior mapping of the physiological condition had been carried out on the same trees by latex diagnosis and foliage characterization (leaf area index). Wood samples were taken for analysis of the reserves (starch and soluble sugars). These data, which are currently being analysed, will form the basis for modelling relations between rubber production and tree growth, notably by establishing a relevant harvesting index.