Plants of Lupinus albus L., cv. Ultra, were grown hydroponically with NO3−-nutrition for 51 d under control (0.05 mol m−3 Na+ and 10 mol m−3 Cl−) and saline (40 mol m−3 NaCI) conditions. Plants were harvested 41 and 51 d after germination and analysed for content and net increment of C, N and the mineral cations K+, Na+, Mg2+, and Ca2+ and the anions Cl−, NOJ, malate, phosphate, and SO42−. Roots, stem interaodes, petioles and leaflets were analysed separately. During the study period net photosynthesis, respiratory losses of CO2 from shoot and root and the composition of the spontaneously bleeding phloem sap and the root pressure xylem exudate were also determined. Using molar ratios of C over N in the transport fluids, increments of C and N, and photosynthetic gains as well as respiratory losses of C, the net flows of C and N in the xylem and phloem were then calculated as in earlier studies (Pate, Layzell and McNeill, 1979a). Knowing the carbon flows, the ratios of ion to carbon in the phloem sap, and ion increments in individual organs, net flows of K+, Na+, and Cl− over the study period were also calculated. Salt stress led to a general decrease of all partial components of C and N partitioning indicating that inhibitions were not due to specific effects of NaCI salinity on photosynthesis or on NO3 uptake. However, there were differences between variously aged organs, and net phloem export of nitrogenous compounds from ageing leaves was substantially enhanced under saline conditions. In addition, NO3−reduction in the roots was specifically inhibited. Uptake and xylem transport of K+ was more severely inhibited than photosynthetic carbon gain or NO3− uptake by the root. K+ transport in the phloem was even more severely restricted under saline conditions. Na+ and Cl− flows and uptake, on the other hand, were substantially increased in the presence of salt and, in particular, there were then massive flows of Na− in the phloem. The results are discussed in relation to the causes of salt sensitivity of Lupinus albus. The data suggest that both a restriction of K+ supply and a strongly increased phloem translocation of Na+ contribute to the adverse effects of salt in this species. Restriction of K+ supply occurs by diminished K+ uptake and even more by reduced K+ cycling within the plant.