 Inclusion Criteria: - MaleFemale outpatients 18 years of age with chronic low back pain. Exclusion Criteria: - You have a serious or unstable disease of the heart or blood vessels, liver, kidney, lungs, or blood-related illness, problems with decreased blood flow to arms and legs peripheral vascular disease, or other medical conditions, or psychiatric conditions that, in the opinion of the investigator, would affect your participation or be likely to lead to hospitalization during the course of the study. - Have acute liver injury such as hepatitis or severe cirrhosis. - Have had previous exposure to duloxetine. - Have a body mass index BMI over 40. - Have major depressive disorder. - Require daily narcotics. 