OBJECTIVE:To identify predictors for back pain, leg pain, and activity limitation in patients with early persistent low back disorders (LBDs). DESIGN:Prospective inception cohort study. SETTING:Primary care private physiotherapy clinics in Melbourne, Australia. PARTICIPANTS:Individuals (N=300) aged 18-65 years with low back and/or referred leg pain of ≥6 weeks and ≤6 months duration. INTERVENTIONS:Not applicable. MAIN OUTCOME MEASURES:Numeric rating scales for back pain and leg pain as well as the Oswestry Disability Scale. RESULTS:Prognostic factors included sociodemographics, treatment related factors, subjective/physical examination, subgrouping factors, and standardized questionnaires. Univariate analysis followed by generalized estimating equations were used to develop a multivariate prognostic model for back pain, leg pain, and activity limitation. Fifty-eight prognostic factors progressed to the multivariate stage where 15 showed significant (P<.05) associations with at least 1 of the 3 outcomes. There were 5 indicators of positive outcome (2 types of LBD subgroups, paresthesia below waist, walking as an easing factor, and low transversus abdominis tone) and 10 indicators of negative outcome (both parents born overseas, deep leg symptoms, longer sick leave duration, high multifidus tone, clinically determined inflammation, higher back and leg pain severity, lower lifting capacity, lower work capacity, and higher pain drawing percentage coverage). The preliminary model identifying predictors of LBDs explained up to 37% of the variance in outcome. CONCLUSIONS:This study evaluated a comprehensive range of prognostic factors reflective of both the biomedical and psychosocial domains of LBDs. The preliminary multivariate model requires further validation before being considered for clinical use.