© 2010 S. Karger AG, Basel. Background/Aims: To determine if aging cobalt-60 sources impact treatment outcomes in patients treated with face pain. Methods: From October 1995 to August 2005, 350 patients with facial pain were treated at the UAB Highlands Gamma Knife® unit. Response data are available for 308 patients. The Leksell Gamma Knife® Model U was used from October 1995 to December 2003 without a source change. The Model C unit has been used since March 2004. From 1995 to 1998 the 50% isodose line of a 4-mm collimator was placed at the nerve root entry zone and 35 Gy was used. Since 1999, 40 Gy has been used. Two-sample t test or Wilcoxon rank sum test was applied to compare continuous variables between groups. A multivariate logistic regression analysis was applied to examine factors related to response. Results: Logistic regression analysis identified age and pain type as independent variables with odds ratios of 1.2 and 3.53, respectively, and p values of 0.0074 and <0.0001, respectively. In the univariate analysis dose also infl uenced response with a p value of 0.0184. Patients treated from October 1995 to October 2000 had a complete response/good response of 66 vs. 60% for patients treated from November 2000 to January 2004 (p = 0.2770). Conclusion: There was no obvious evidence that aging cobalt-60 sources infl uenced response in our patients with facial pain.