Rat bite fever, caused by Streptobacillus moniliformis, is a systemic illness 
classically characterized by fever, rigors, and polyarthralgias. If left 
untreated, it carries a mortality rate of 10%. Unfortunately, its nonspecific 
initial presentation combined with difficulties in culturing its causative 
organism produces a significant risk of delay or failure in diagnosis. The 
increasing popularity of rats and other rodents as pets, together with the risk 
of invasive or fatal disease, demands increased attention to rat bite fever as a 
potential diagnosis. The clinical and biological features of rat bite fever and 
Streptobacillus moniliformis are reviewed, providing some distinguishing 
features to assist the clinician and microbiologist in diagnosis.