An irrigation experiment with water of different salinities (2.8, 7.6 and 12.7 tool C1 m -a) was carried out from 1982 to 1988 in a mature "Shamouti" orange grove in the coastal plain of Israel. Seasonal accumulation of salts in the soil solution of the root zone (EC of more than 4.0 dS m-1 at the end of the irrigation season) was almost totally leached during the winter. The average annual rainfall of 550 mm reduced EC values below 1.0 dS m-1. Tree growth, as measured by the increase in cross sectional area of main branches, was retarded by saline irrigation water (123, 107 and 99 cm 2 growth per tree during six years for the 2.8, 7.6 and 12.7 mol C1 m-3 treatments, respectively). Potassium fertilization (360 kg K20 ha -1) increased yield at all salinity levels during the last three years of the experiment, mainly by increasing fruit size. Saline irrigation water slightly increased sucrose and C1 concentrations in the fruit juice. Salinity decreased transpiration, increased soil water potential before irrigation and decreased leaf water potential. However, the changes in leaf water potential were small. Leaf C1 and Na concentrations increased gradually during the experimental period, but did not reach toxic levels up to the end of the experiment (4.4 g C1 kg-1 dry matter in the high salt treatment vs. 1.7 in the control). Relatively more leaf shedding occurred in the salinized trees as compared to the control. The sour orange rootstock apparently provided an effective barrier to NaC1 uptake; therefore, the main effect of salinity was probably osmotic in nature. No interactions were found between N or K fertilization and salinity. Additional N fertilization (160 kg N ha-1 over and above the 200 kg in the control) did not reduce C1 absorption nor did it affect yield or fruit quality. Additional K had no effect on Na absorption but yield and fruit size were increased at all salinity levels. No significant differences were obtained between partial and complete soil surface wetting (30% and 90% of the total soil area resp.) with the same amounts of irrigation water. The effect of salinity on yield over the six years of the experiment was relatively small and occurred Offprint requests to: S. Dasberg only after some years. But, in the last three years salinity significantly reduced average yields to 74.6, 67.1, and 64.2 Mg ha-1 for the three levels of salinity, respectively.These results suggest that saline waters of up to 13 mol C1 m-3 primarily influence the tree water uptake and growth response of "Shamouti" orange trees, whereas yield was only slightly reduced during six years.The effect of salinity on citrus culture was comprehensively reviewed by Bernstein (1969). He concluded that salt tolerance was very much dependent on rootstock: sour orange and rough lemon were less sensitive than sweet lime and Troyer citrange while Cleopatra mandarin was the most tolerant. Large differences in C1 and Na uptake by different citrus rootstocks were subsequently reported by Grieve and Walker (1983). A survey of citrus orchard...