Three experiments were conducted in a heated glasshouse on plants of Brassica juncea cv. Canadian Black and rape cv. Drakkar grown in pots of washed river sand with a water holding capacity of 21%. In experiment 1, water stress was imposed by withholding water 24 d after seedling emergence and at the beginning of flowering. Stress was relieved after 13 d and again after visible wilting at the beginning of flowering. In experiments 2 and 3, water was withheld at floral bud appearance, at full flowering and at pod formation. Rewatering took place after 6 d in experiment 2 and after visible wilting in experiment 3. Water stress decreased the leaf expansion rate compared with watered plants. The relative rate of leaf expansion was linearly related to relative water content, leaf potential and turgor potential. Leaf mortality was hastened by stress and was greater in B. juncea than in rape. The reduction in leaf expansion rate due to low tissue water status at early stages and the accelerated senescence and mortality of older leaves at later stages of growth decreased the total green leaf area.