1. Glomerulonephritis was produced in rabbits by the injection of antirabbit-kidney duck serum.
2. The clinical and pathologic characteristics of the disease are discussed.
3. It was found possible by appropriate means either to accelerate the development of the nephritis or to prevent its appearance entirely.
4. An apparent correlation was found between the development of the nephritis and the formation of antibodies to duck serum by the injected rabbit.
5. The generally accepted concept of the mechanism of the disease does not appear to be in accordance with the facts here observed. A new hypothesis is presented.