Abstract 1. 1. Using isotopically labeled sugars the transport kinetics of glucose uptake and the inhibitory effect of mannose, sorbose, fructose, galactose, glucosamine and 3-0-methyl glucose on glucose uptake have been studied in Trypanosoma lewisi. 2. 2. The inhibitory activity of these carbohydrates on one another has also been examined. 3. 3. The results of these experiments suggest that the sites of sugar reaction with the transport mechanism(s) may be qualitatively different from known analogous mechanisms in metazoan organisms. 4. 4. Two possible sites for carbohydrates transport in T. lewisi have been proposed.