Field experiments were carried our for three years at Montpellier, France in a deep collovial alluvial soil during summer to study biomass production of grain sorghum (Sorghum bicolor (L.) Moench) under water stress. All treatments were well watered at sowing to ensure good crop emergence. Grain sorghum biomass showed substantial variation between treatments. Grain yields varied from 3.8 tha(-1) in highly stressed treatment to 10.7 tha(-1) in well watered treatment. The number of panicles per unit area was greatly influenced by the level of water regime at booting stage. Water deficit at maturity affects seed weight. However. a compensatory effect was observed on the yield components of sorghum under the different treatments owing to differences in plant population. (C) 1997 Elsevier Science Ltd.