Background: Accurate assessment of the need for admission is challenging in out-of-hours (OOH) primary care. Understanding more about patient contacts where the decision to continue care in the community may have been incorrect could assist clinicians in assessing clinical risk., Aim: To define the population contacting OOH primary care who are at higher risk of re-presenting to this service and requiring urgent transfer to secondary care within 3 days of their initial contact., Design and Setting: Retrospective service evaluation of 4 years of patient contacts with Oxfordshire OOH primary care., Method: Multivariable logistic regression was used to evaluate demographic and service delivery factors associated with increased risk of delayed escalation to secondary care., Results: Almost 1% of 496 931 patients contacting OOH primary care required escalation to secondary care within 3 days. Of these, 68.5% were initially discharged with no follow-up or advice to contact their GP; 14.7% were initially referred to secondary care. The odds of requiring escalation were increased with age (odds ratio [OR] 1.010; 95% confidence interval [CI] = 1.009 to 1.011; P<0.001), more frequent prior use of the OOH service (OR 1.016; 95% CI = 1.010 to 1.021; P<0.001), and presenting during periods of low call volume (OR 0.880; 95% CI = 0.857 to 0.904; P<0.001)., Conclusion: Older, prior users of the service, presenting at less busy times, are at greater risk of requiring secondary care referral from the OOH service within 3 days of their initial contact. These higher-risk patient groups might benefit from active follow-up by the OOH service., (© British Journal of General Practice 2017.)