This is a double-blind, double-dummy, multicenter, randomized, active-controlled, parallel group, outpatient, safety study to evaluate the long term safety of arformoterol in the treatment of subjects with COPD. Study participation will be over approximately 6 months. This study was previously posted by Sepracor Inc. In October 2009, Sepracor Inc. was acquired by Dainippon Sumitomo Pharma., and in October 2010, Sepracor Inc's name was changed to Sunovion Pharmaceuticals Inc.