Considerable uptake of phosphate by both the shoot and root has been demonstrated for young barley plants with their roots in anoxic culture solution at concentrations of 1 to 10 μM orthophosphate. Consideration of the free space and passive transpirational uptake indicates an accumulatory process, and the immediate efflux caused by respiratory inhibitors supports this. Shoot uptake is much less at higher external concentrations of phosphate and at o.I mM was only 14 per cent of the control. The root accumulation process was unimpaired at an external concentration of 1 μM phosphate when the whole plant was subjected to anaerobic conditions (shoot illuminated) but under similar conditions at a concentration of 100 μM a considerable efflux of phosphate occurred. Analysis of the fate of phosphate taken up from anoxic solution of phosphate (10 μM) indicated that there was a reduction in the level of inorganic phosphate after 4.5 h and steady rise in sugar phosphates up to 6 h with a marked increase in the levels of glucose-6-phosphate, fructose-6-phosphate, and the phosphoglycerate fraction.