OBJECTIVES: Guidelines for primary care management of LBP in primary care recommend an initial period of watchful waiting before referral to PT.  Some evidence suggests early PT may reduce future health care costs for LBP.  This study compared LBP-related costs over a 1-year period in patients with acute LBP randomly assigned to usual care versus early PT. METHODS: Adults (age 18-60) visiting primary care with acute, non-specific LBP were recruited.  All participants received advice and education about LBP and were randomized to 4 PT sessions or watchful waiting for 4 weeks.  Clinical outcomes and LBP-related costs were collected monthly for 1 year after enrollment using online diaries of health care utilization and work loss due to LBP. RESULTS: CONCLUSIONS: Early PT showed small benefits in pain reduction across 1-year. The incremental cost effectiveness ratio may exceed willingness to pay thresholds.