Summary1. Human red cells and serum are unfavorable to the growth of Leishmania donovani.2. A method is given for removing the red cells and serum from blood before planting.3. By this method blood cultures have been obtained from nine out of ten samples of blood from five patients, some of them after considerable antimony treatment.4. A modified “N.N.N.” medium is suggested.5. On this medium the Leishman-Donovan bodies from spleen punctures or peripheral blood develop into flagellates at all hydrogen-ion concentrations tested, i.e., between PH 6.8 and PH 8.2 and the flagellates grow at least to PH 9.0.6. Cultures on this modified medium show post-flagellate forms and perhaps Cornwall's “thick tails.”