1. Complaints that the present method of immunization against bluetongue is not safe and that it produces an inadequate immunity have been justified.
2. A plurality of antigenically different virus strains has been established.
3. There appears to be an antigenic component common to all strains
investigated and in addition an unknown number of different specific components.
4. There is a wide variation in the virulence of different strains.
5. The virus is not attenuated by serial passage through sheep.
6. The significance of these findings is discussed.