The use of bicyclic carbohydrates for the treatment of parasite infections is described. Different bicyclic carbohydrates have been tested in vitro against a number of protozoa. These compounds also have been screened against viruses, tumors, bacteria and fungi. Compound A1, a thiophenyl-containing bicyclic carbohydrate possessed significant activity against Trypanosoma brucei rhodiense, a parasite that causes the lethal sleeping sickness. Compound A2 and Compound A3, bicyclic carbohydrates with halogen containing aryl groups, possessed significant activity against Leishmania donovani, a parasite that causes leishmaniasis. Bicyclic carbohydrates in general, and Compound A1, Compound A2 and Compound A3 more specifically, could be possible treatments for the sleeping sickness and leishmaniasis in the future.