1. The water relations of Glycyrrhiza glabra L. under desert conditions, including the water expenditure, osmotic pressure of the plant sap and the water saturation deficit, were studied in different localities. 2. Transpiration measurements have shown that the plant transpires at relatively higher rates than desert plants. The curves of diurnal march of the transpiration and those of the stomatal aperture showed almost the same trend, indicating a strong stomatal control on transpiration. There is lack of parallelism between both curves and those of the climatic factors, particularly in dry months. 3. Two types of transpiration curves have been recognised, viz. the single-peaked curves with early maximum in dry months and the dome-shaped curves without prominant peak in months with mild climatic conditions. 4. Comparison of the mean monthly transpiration rates in two localities revealed that the transpiration was higher in the locality with better water supply. Generally, there is a discrepancy between the mean values of transpiration and those of vapour pressure deficit and evaporation. 5. The plant exhibited high values of osmotic pressure and water saturation deficit which increased by the progress of the growing season. These values were higher in the locality with relatively low available soil moisture. The plant has been found to withstand high water deficits for long periods. 6. The mechanisms by which the plant is endowed for drought endurance are discussed.