BACKGROUND: In many countries emergency departments (EDs) are facing an increase in demand for services, long waits, and severe crowding. One response to mitigate overcrowding has been to provide primary care services alongside or within hospital EDs for patients with non-urgent problems. However, it is unknown how this impacts the quality of patient care and the utilisation of hospital resources, or if it is cost-effective. This is the first update of the original Cochrane Review published in 2012. OBJECTIVES: To assess the effects of locating primary care professionals in hospital EDs to provide care for patients with non-urgent health problems, compared with care provided by regularly scheduled emergency physicians (EPs). SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (the Cochrane Library; 2017, Issue 4), MEDLINE, Embase, CINAHL, PsycINFO, and King's Fund, from inception until 10 May 2017. We searched ClinicalTrials.gov and the WHO ICTRP for registered clinical trials, and screened reference lists of included papers and relevant systematic reviews. SELECTION CRITERIA: Randomised trials, non-randomised trials, controlled before-after studies, and interrupted time series studies that evaluated the effectiveness of introducing primary care professionals to hospital EDs attending to patients with non-urgent conditions, as compared to the care provided by regularly scheduled EPs.  DATA COLLECTION AND ANALYSIS: We used standard methodological procedures expected by Cochrane. MAIN RESULTS: We identified four trials (one randomised trial and three non-randomised trials), one of which is newly identified in this update, involving a total of 11,463 patients, 16 general practitioners (GPs), 9 emergency nurse practitioners (NPs), and 69 EPs. These studies evaluated the effects of introducing GPs or emergency NPs to provide care to patients with non-urgent problems in the ED, as compared to EPs for outcomes such as resource use. The studies were conducted in Ireland, the UK, and Australia, and had an overall high or unclear risk of bias. The outcomes investigated were similar across studies, and there was considerable variation in the triage system used, the level of expertise and experience of the medical practitioners, and type of hospital (urban teaching, suburban community hospital). Main sources of funding were national or regional health authorities and a medical research funding body.There was high heterogeneity across studies, which precluded pooling data. It is uncertain whether the intervention reduces time from arrival to clinical assessment and treatment or total length of ED stay (1 study; 260 participants), admissions to hospital, diagnostic tests, treatments given, or consultations or referrals to hospital-based specialist (3 studies; 11,203 participants), as well as costs (2 studies; 9325 participants), as we assessed the evidence as being of very low-certainty for all outcomes.No data were reported on adverse events (such as ED returns and mortality). AUTHORS' CONCLUSIONS: We assessed the evidence from the four included studies as of very low-certainty overall, as the results are inconsistent and safety has not been examined. The evidence is insufficient to draw conclusions for practice or policy regarding the effectiveness and safety of care provided to non-urgent patients by GPs and NPs versus EPs in the ED to mitigate problems of overcrowding, wait times, and patient flow.