Does a stratified primary care approach for patients with low back pain result in clinical and economic benefits when compared with current best practice? A randomised, controlled trial with stratification for three risk groups and a targeted treatment according to the risk profile. Group allocation was carried out by computer-generated block randomisation in a 2:1 ratio. Ten general practices in England. Men and women at least 18 years old with low back pain of any duration, with or without associated radiculopathy. Exclusion criteria were potentially serious disorders, serious illness or comorbidity, spinal surgery in the past 6 months, pregnancy, and receiving back treatments (except primary care). In the intervention group decisions about referral to risk group were made by use of the STarT Back Screening Tool. The 30-min assessment and initial treatment focused on promotion of appropriate levels of activity, including return to work, a pamphlet about local exercise venues and self-help groups, the Back Book, and a 15-min educational video Get Back Active. Low-risk patients were only given this clinic session. Medium-risk patients were referred for standardised physiotherapy to address symptoms and function. High-risk patients were referred for psychologically informed physiotherapy to address physical symptoms and function, and psychosocial obstacles to recovery. In the control group a 30-min physiotherapy assessment and initial treatment including advice and exercises was provided, with the option of onward referral to further physiotherapy, based on the physiotherapist's clinical judgement. The 12 months score of Roland and Morris Disability Questionnaire (RMDQ). Secondary measures were referral for further physiotherapy, back pain intensity, pain catastrophising, fear-avoidance beliefs, anxiety, depression, health-related quality of life, reduction of risk-subgroup, global change of pain, number of physiotherapy treatment sessions, adverse events, health-care resource use and costs over 12 months, number of days off work because of back pain, and satisfaction with care. Of 851 patients assigned to the intervention (n=568) and control groups (n=283) a total of 649 completed the 12 months follow-up. Adjusted mean changes in RMDQ scores were significantly higher in the intervention group than in the control group at 4 months (4.7 [SD 5.9] vs 3.0 [5.9], between-group difference 1.8 [95% CI 1.6 to 2.6]) and at 12 months (4.3 [6.4] vs 3.3 [6.2], 1.1 [0.6 to 1.9]). At 12 months, stratified care was associated with a mean increase in generic health benefit (0.039 additional QALYs) and cost savings (£240.01 vs £274.40) compared with the control group. There were significant differences in favour of the intervention group in many of the secondary outcomes. A stratified management approach including a prognostic screening and treatment targeting, showed improved clinical and economic benefits when compared with current best practice.