OBJECTIVES: To identify lower back pain (LBP) patients who use narcotic medications and examine their medication behaviors, medical and pharmacy claim costs and associated comorbidities. METHODS: This study used medical and pharmacy claims data from 165,569 employees ages 18 to 64 years from three employer groups from September 2002 to December 2003. LBP patients were identified using ICD-9 diagnosis codes from medical claims data. Differences in costs and comorbidities were examined between LBP patients who use narcotic medications and LBP patients who do not use narcotic medications. RESULTS: Among eligible members, 13,760 (8.3%) were identified as LBP patients. Nearly 60% were female with an average age of 46.8 years. Approximately half of the LBP patients (44.8%) used narcotic medications; however, they consumed 71% of total health care costs (medical plus pharmacy costs) among LBP patients. The average monthly total healthcare cost for a narcotic-using LBP patient was $1,040 versus $347 for a LBP patient without narcotics. Narcotic-using LBP patients had significantly (p CONCLUSION: Lower back pain patients who use narcotic medications are more likely to have additional health conditions and higher healthcare costs than non-narcotic using LBP patients. Further, patients with comorbid anxiety or depression take more narcotics than those with other comorbidities.