Gonococci possess a common heat stable antigen that is not identical to endotoxin. 2. A model of gonococcal peritonitis is described that simulates human disease in its progression from local to disseminated infection and its milieu of mucin and hemoglobin. 3. Vaccination with the heat stable antigen protected against disseminated infection and raised the LD50s from 100 to 1000-fold. 4. Vaccination with antigen from one strain of gonococci conferred protection against heterologous infection. 5. This protection did not require pili antigens or bactericidal antibody. 6. Protection in vaccinated mice resulted from a rapid, intense, and chemotactically-mediated influx of PMNs that eradicates the local infection.
