The rates of glucose uptake by some species of plankton were deternined by 3 H-glucose tracer method. Experimental results indicated that the observed glucose uptake at natural scawatcr concentrations by Platymonas subcordiformis and Brachionus plicatilis was principally a metabolic process fitted with the Michachs-Menten equation in the range of adaptive temperatures. Heterotrophic ubtake by platymonas subcordformis was unainly dependent on diffusion at high glucose levels. The uptake by Brachionus plicatilis showed active transport even at bigh glucose levels, indicating its high beterotrophic activity. The uptake rate by Artemia salina was lower. and its Vm/K ratio was lower than those of the other two species of plankton.