Study Design. Within-study cost-utility analysis.Objectives. To explore the cost-utility of implementing stratified care for low back pain (LBP) in general practice, compared with usual care, within risk-defined patient subgroups (that is, patients at low, medium and high risk of persistent disabling pain).Summary of Background Data. Individual-level data collected alongside a prospective, sequential comparison of separate patient cohorts with six-month follow-up.Methods. Adopting a cost-utility framework, the base case analysis estimated the incremental LBP-related healthcare cost per additional quality-adjusted life year (QALY) by risk subgroup. QALYs were constructed from responses to the three-level EQ-5D, a preference-based health-related quality of life instrument. Uncertainty was explored with cost-utility planes and acceptability curves. Sensitivity analyses examined alternative methodological approaches, including a complete case analysis, the incorporation of non-back pain-related healthcare use and estimation of societal costs relating to work absence.Results. Stratified care was a dominant treatment strategy compared with usual care for patients at high risk, with mean healthcare cost savings of £124 and an incremental QALY estimate of 0.023. The likelihood that stratified care provides a cost-effective use of resources for patients at low and medium risk is no greater than 60% irrespective of a decision makers' willingness-to-pay for additional QALYs. Patients at medium and high risk of persistent disability in paid employment at six-month follow-up reported, on average, six fewer days of LBP-related work absence in the stratified care cohort compared with usual care (associated societal cost savings per employed patient of £736 and £652, respectively).Conclusions. At the observed level of adherence to screening tool recommendations for matched treatments, stratified care for LBP is cost-effective for patients at high risk of persistent disabling LBP only.