In 2005, our initial analysis of the impact on health care costs (HCC) of providing on-site nurse practitioner (NP) services showed favorable results. We measured the effects of the NP program on HCC in two ways. Method 1 compared actual HCC for 2005 to 2007 versus projected HCC, the latter based on medical payments in 2002 to 2004, before the NP intervention. Method 2 was a microanalytic comparison of the HCC of nine major diagnostic categories responsible for 88.5% of all conditions treated by the NP from July 2005 to December 2006. Annualized cost of the NP program was $124,750. Savings in HCC using the first method were $1,089,466 per year, yielding a benefit-to-cost ratio of 8.7 to 1. Savings in HCC using the second method reflected a ratio of 2.0 to 1. In addition, method 1 reflects HCC savings which may be due to the addition of a 24/7 nurse help line. This 3-year analysis confirms our preliminary findings that an on-site NP has a favorable benefit-to-cost function. Longer-term analyses are needed to confirm these findings.