This paper presents a review of literature on the impact of the medical emergency team (MET) on inpatient mortality,cardiopulmonary arrests or unscheduled intensive care unit (ICU) admissions. A total of 14 172 abstracts and 98 full text papers were reviewed. In total, 24 met the inclusion criteria, 2 used a cluster-randomized controlled trial, 11 before and after, 6 retrospective analyses, 4 prospective cohorts and 1 not reported. There is moderate to strong evidence that METs are associated with decreased mortality and cardiac arrest rates, and weak evidence on its impact on ICU admission rate reductions. This evidence suffers from the flaws with only two randomized controlled trials examining differing outcome measures with differing results. Poor methodology and failure to report both quality improvement co-interventions and time response rates of METs, limit the strength of the evidence that METs are effective interventions for preventing mortality, code rates or unscheduled ICU admissions. Studies with improved implementation practices and evaluation of the efficacy of MET is warranted.