At the end of the Run-In Period, subjects will return to the Clinic and who meet all of the Randomization Criteria will be randomized to double-blind study medication (12-week treatment period). Subjects will be randomized to receive either FF/VI 100/25 via NDPI or Fluticasone Propionate/Salmeterol 250/50mcg via ACCUHALER/DISKUS. Matching placebos will be available in NDPI and ACCUHALER/DISKUS. Each morning (approximately 6-10 AM) subjects will take 1 inhalation from the NDPI followed by 1 inhalation from the ACCUHALER/DISKUS. Each evening (approximately 6-10 PM), approximately 12 hours after the morning dose with blinded study medication, subjects will take 1 inhalation from the ACCUHALER/DISKUS. Subjects will return to the clinic at the end of the treatment period.