Glucose transport into human peripheral lymphocytes, rat lymphocytes, and rat thymocytes were investigated using 2-deoxyglucose (2-DOG) in the transport studies. Our results showed rat thymocytes to have a high affinity and a low affinity system for transporting 2-DOG with Km values of0.11 mM and 7.14 mM respectively. Both of the systems were inhibited by phloretin (0.1 mM), a specific inhibitor of carrier mediated transport. Human peripheral lymphocytes and rat lymphoctes transported 2-DOG with Km values of 5.26 mM and 3.57 mM respectively. While insulin had no effect on this transport in thymocytes and lymphocytes, it inhibited the efflux of 2-DOG from the cells.