This note reports the results of experiments aimed at confirming the luxury uptake of phosphorus (P) by sediment bacteria as polyphosphate (Poly-P). Aerobic suspensions of sediments from two different sites were spiked with 1 mg P/L as orthophosphate and augmented with acetate (a fermentation product) or glucose. The orthophosphate was rapidly taken up over a period of a few hours. When these aerobic uptake experiments were made anaerobic and additional organic carbon added, only the acetate-amended sediment released a significant amount of the added phosphorus. It was hypothesised that during the aerobic stage, and with the addition of acetate, some of the phosphorus was accumulated as Poly-P by sediment microorganisms, which was released during the subsequent anaerobic stage (provided acetate was still present). Two lines of evidence--transmission electron microscope analysis of sediment bacteria and 31P-NMR analysis of sediment extracts--are presented to support the hypothesis that a portion of the phosphorus taken up during the aerobic experiments was stored as Poly-P.