An acute inflammatory response was induced in rabbits by an intramuscular injection of turpentine. After this injection serial serum samples were obtained and serum haptoglobin levels were monitored. In addition, increased antibacterial activity was measured using a viable plate and photometric growth assay. As early as 4 hrs after turpentine challenge an increase was noted in serum antibacterial activity towards Staphylococcus aureus. At 48 hrs pronounced killing activity was demonstrated against S. aureus and S. epidermidis but not against Escherichia coli or other gram negative bacilli. By five days another serum bactericidal activity was present against Bacillus subtilis. Enhanced serum antibacterial activity persisted for 2 weeks. Partial characterization of these factors indicates that they are probably beta lysins.