There is growing concern in the United States about the excessive use of rabies post exposure prophylaxis (PEP) treatment. In this paper we have estimated the cost effectiveness of rabies PEP treatment under various scenarios of rabies transmission. When the risk of a patient getting rabies is deemed greater than 0.7%, then giving PEP will be cost saving (societal perspective). For lower risks of transmission, cost effectiveness estimates ranged from approximately $500,000 per life saved to $billions. The uncertainty caused by the wide range of cost effectiveness can only be resolved through analysis of data describing rabies transmission risk in a variety of scenarios.