Factors which affect the phosphorus uptake activity of the phosphorus-accumulating bacterium, strain NM-1, were studied. Cells harvested during logarithmic growth phase took up a large amount of phosphorus under aerobic conditions. However, cells harvested during Stationary phase had decreased phosphorus uptake activity, especially in late stationary phase. By increasing the intracellular carhohydrate content beforehand, cells harvested in early stationary phase exhibited recovered activity, while cells harvested in late stationary phase did not take up phosphorus although they did accumulate carbohydrate.