It is shown, in a carefully controlled experiment, that fowl leucemia can be readily transmitted from chicken to chicken by injection. Of 25 fowls, 13 were injected intravenously with blood from a chicken (No. 575) with erythroleucosis and 12 with blood from a chicken (No. 689) with myeloid leucosis. The injected birds and an equal number of uninjected controls were kept in tiers of alternating cages under as nearly identical conditions as possible. The donors, the controls, and the injected birds were all of the same stock and of the same age. In the two series 13 or 52 per cent of the 25 fowls inoculated developed leucemia within 4 to 10 weeks after injection. The two types of leucemia, erythroleucosis and myeloid leucosis, developed in both groups irrespective of the type used for injection. Among the uninjected controls no cases of erythroleucosis or of myeloid leucosis were observed. Lymphoid leucosis occurred in one injected fowl but since it also occurred in one control it may be assumed that it was probably not caused by the injected material.