Background: Effective collaboration and teamwork is essential to providing safe hospital care. The objective of this study was to assess the effect of an intervention designed to improve interdisciplinary collaboration and lower the rate of adverse events (AEs). Methods: The study was a controlled trial of an intervention, Structured Inter-Disciplinary Rounds, implemented in 1 of 2 similar medical teaching units in a tertiary care academic hospital. The intervention combined a structured format for communication with a forum for regular interdisciplinary meetings. We conducted a retrospective medical record review evaluating 370 randomly selected patients admitted to the intervention and control units (n=185 each) in the 24 weeks after and 185 admitted to the intervention unit in the 24 weeks before the implementation of Structured Inter-Disciplinary Rounds (N=555). Medical records were screened for AEs.Twohospitalists confirmed the presence of AEs and assessed their preventability and severity in a masked fashion. We used multivariable Poisson regression models to compare theadjusted incidence of AEs in the intervention unit to that in concurrent and historic control units. Results: The rate of AEs was 3.9 per 100 patient-days for the intervention unit compared with 7.2 and 7.7 per 100 patient-days, respectively, for the concurrent and historic control units (adjusted rate ratio, 0.54; P=.005; and 0.51; P=.001). The rate of preventable AEs was 0.9 per 100 patient-days for the intervention unit compared with 2.8 and 2.1 per 100 patient-days for the concurrent and historic control units (adjusted rate ratio, 0.27; P=.002; and 0.37; P=.02). The low number of AEs rated as serious or life-threatening precluded statistical analysis for differences in rates of events classified as serious or serious and preventable. Conclusion: Structured Inter-Disciplinary Rounds significantly reduced the adjusted rate of AEs in a medical teaching unit.