Inclusion Criteria:  Must reside within the contiguous 48 United States or District of Columbia Must provide a valid, government-issued identification with photo and birthdate Must have Internet access or telephone service to communicate with registry staff Must have sufficient English language proficiency to complete case report forms independently or with assistance from registry staff Must have a primary care physician or other physician who regularly provides health care Must provide the name, dose, and frequency of use of all current medications Case participants must have chronic low back pain Control participants must be free of any chronic pain and may include healthy volunteers  Exclusion Criteria:  Must not be pregnant Must not reside in an institutional facility