Leishmania braziliensis, L. mexicana, and L. garnhami were studied for their ability to produce American cutaneous leishmaniasis, using C57B1/6 female mice as the animal model. No significant difference in the clinical course of mouse foot pad infection was found between the three American Leishmania species studied. In general, the incubation period varied from 2–4 weeks. Mice developed only local swelling and sometimes ulceration at the sites of inoculation. After 4 weeks of progress lesions began to decrease without obvious impact on the general health of the mice. When glucan immunotherapy (120–240 mg/kg body weight) was initiated previous to, or simultaneously with, infection the development of foot pad lesions was not significantly inhibited, this despite clear evidence of generalized stimulation of the reticuloendothelial system. On the other hand, pentavalent antimony at high doses (1,000–1,500 mg/kg) induced only a significant lengthening of the latent period. However, different combinations of glucan and pentavalent antimony (various doses of each drug, timing of administration, or changes in the sequence of use of both drugs) did not significantly alter the clinical course of American Leishmania infection as compared with pentavalent antimony alone. Thus, not only were glucan or glucantime alone unable to cure the infection (as evidenced by some animals which showed rapidly growing lesions some time after the end of treatment), but no potentiation was observed.