The purpose of this protocol is to examine whether mifepristone, a medication with glucocorticoid receptor antagonist activity, may be a potential treatment for Tobacco Use Disorder (TUD). Mifepristone has already shown promise as a potential treatment for PTSD (1) and alcohol use disorder (AUD) (2), but no previous studies have examined the therapeutic potential of mifepristone for TUD. This will be a double-blind, placebo-controlled study on the effects of a 7-day treatment with 600 mg mifepristone, or placebo, on cognitive function, tobacco withdrawal severity, and smoking behavior.