Summary and Conclusions Two arthropod strains, two human strains, and one armadillo strain of Trypanosoma cruzi were studied to determine their cultural and biochemical characteristics and their growth requirements. The observations have permitted the following conclusions: 1. There was abundant growth and multiplication in thirteen sugars, all of which showed no fermentation or gas production, i.e., the growth is eugonic. 2. Methyl red and Voges-Prouskauer tests were negative; indol and H2S were not produced. 3. Growth in milk was feeble and no changes were observed. 4. The thermal death point at 40°C. was more than three and a half hours, but at 45°C. was between 15 and 30 minutes. 5. The organisms were essentially bile insoluble, but dissolved in 96 hours. 6. Thiamin chloride, nicotinic acid and pyridoxin had temporary growth-stimulating properties, ascorbic acid had none, and riboflavin and calcium pantothenate were toxic. 7. The essential fraction for growth was apparently present in the serum and red blood cells, but was not vitamin B complex or vitamin C. 8. On leishmania blood agar, T. cruzi formed large colonies. 9. An egg-liver extract medium has been described for the cultivation of hemoflagellates.