[en] Root chicory (Cichorium intybus var. sativum) is a cash crop cultivated for inulin production in Western Europe. This plant could be exposed to severe water stress during the three last months of their six months growing period. The aim of this study was to quantify the effect of a progressive decline in water availability on plant growth, photosynthesis and sugar metabolism and to determine its impact on inulin production. Water stress drastically decreased root fresh and dry weight, leaf number, total leaf area and stomatal conductance. Stressed plants, however, increased their water use efficiency, decreased the shoot to root ratio and lowered their osmotic potential through soluble sugar accumulation. Despite a decrease in photosynthetic pigments, the light phase of the photosynthesis remained unaffected under water stress. Water stress increased sucrose phosphate synthase (SPS) activity in the leaves, but not in the roots. Water stress inhibited sucrose:sucrose 1-fructosyltransferase (1-SST) and fructan:fructan 1 fructosyltransferase (1—FFT) after 19 weeks of culture and slightly increased fructan 1-exohydrolase activities (1-FEH). The root inulin concentration and the mean degree of polymerisation (DP) of the inulin chain remained however unaffected by water stress. It is concluded that root chicory displayed resistance to water stress, but that such a resistance is obtained at the expense of growth which, in turn, leads to significant decrease in inulin production.