Interhospital transfers for acute surgical care occur commonly, but without clear guidelines or protocols. Transfers may subject patients and delivery systems to significant burdens without clear clinical benefit. The incidence and factors associated with unnecessary transfers are not well described.We conducted a retrospective cohort study of patient transfers within a regional referral network to a tertiary center for nontrauma acute surgical care from 2009 to 2013. Clinically unnecessary transfers were defined as transfers that resulted in no intervention (operation, endoscopy, or interventional radiology procedure) and discharge to home within 72 hours. We performed bivariate and multivariate logistic regression analyses. The study population included 2177 patient transfers, 19 per cent of which were determined to be clinically unnecessary. After adjustment, clinically unnecessary transfers were more commonly performed for patient request (odds ratio 5 2.52, 95% confidence interval 5 1.60-3.99), continuity of care (1.87, 1.44-2.42), and care by urologic (1.50, 1.06-2.13) and vascular services (1.44, 1.03-2.01). Patients with higher comorbidity and severity of illness scores were less likely to have unnecessary transfers. The burden of unnecessary transfers could be mitigated by identifying appropriate transfer candidates through mutually developed guidelines, interfacility collaboration, and increased use of remote care to provide surgical subspecialty consultation and maintain continuity.