BACKGROUND CONTEXT: Treatment guidelines suggest that most acute low back pain (LBP) episodes substantially improve within a few weeks and that immediate use of imaging and aggressive therapies should be avoided. PURPOSE: Assess the actual practice patterns of imaging, noninvasive therapy, medication use, and surgery in patients with LBP, and compare their costs to those of matched controls without LBP. STUDY DESIGN: A retrospective analysis of claims data from 40 self-insured employers in the United States. PATIENT SAMPLE: The study sample included 211,551 patients, aged 18 to 64 years, with one LBP diagnosis or more (per Healthcare Effectiveness Data and Information Set specification) during 2004 to 2006, identified from a claims database. Patients had continuous eligibility for 12 months or more after their index LBP diagnosis (study period), for 6 months or more before their index diagnosis (baseline period), and no other LBP diagnosis during the baseline period. Patients with LBP were matched to a random cohort of patients without LBP by age, gender, employment status, and index year. OUTCOMES MEASURES: Physiological measures (eg, imaging and diagnostic tests), functional measures (eg, pharmacologic and nonpharmacologic treatment for LBP, health-care resource use), and direct (medical and prescription drug) and indirect (disability and medically related absenteeism) costs were assessed within the year after the LBP diagnosis. METHODS: Univariate analyses described treatment patterns and compared baseline characteristics and study period costs. RESULTS: Patients with LBP had significantly higher rates of baseline comorbidities and resource use compared with controls. Of patients with LBP, 41.6% had imaging mean (median) [standard deviation] 34.3 (0) [78.6] days after the LBP diagnosis. Most patients with LBP (69.4%) used medications starting 51.9 (8) [86.2] days after the diagnosis. Opioids were commonly prescribed early (41.6% of patients; after 82.8 (25) [105.9] days). Of patients with LBP, 2.05% had surgery during the study period. Patients with LBP were likely to have chiropractic treatment first, followed by pharmacotherapy with muscle relaxants and nonsteroidal anti-inflammatory drugs. Except for less surgery, these findings also held for patients with only nonspecific LBP. Patients with LBP had higher mean direct costs compared with controls ($7,211 vs. $2,382, respectively; p<.0001), with surgery patients having mean direct costs of $33,931. CONCLUSIONS: Contrary to clinical guidelines, many patients with LBP start incurring significant resource use and associated expenses soon after the index diagnosis. Achieving guideline-concordant care will require substantial changes in LBP practice patterns.