Glucose uptake by whole-cell suspension of the facultative anaerobe Cellulomonas fimi, which was two-fold higher under aerobic conditions than under N2 or H2, was inhibited by inhibitors of electron transport and ATP synthesis and, particularly, by proton and metal ion ionophores. A variety of sugars, including 2-deoxyglucose, did not inhibit glucose uptake but cellobiose was a non-competitive inhibitor. Cells grown on cellobiose medium transported glucose at one half the rate of glucose-grown cells. Cellulomonas fimi has a highly specific active system for glucose transport.