The focus of this paper is to provide an overview of the process and findings of a Cochrane systematic review on Outreach.  The objectives of this review were to determine the impact of Outreach services on hospital mortality rates, ICU admission patterns, length of hospital stay and adverse events.  The criteria for considering studies for the review were clearly identified prospectively in a published protocol (McGaughey et al, 2005).  A comprehensive search strategy of databases, conference proceedings, reference lists, contacting authors of relevant papers and critical care organisations was undertaken to locate the evidence.  All randomised or controlled trials, controlled before and after and interrupted time series designs that met the inclusion criteria for the review were included.  Two studies were included in the review. Data was abstracted and the methodological quality of the included studies was independently reviewed by two authors.  The studies were heterogeneous in terms of interventions, participants, setting and outcomes.  The methodological quality of the studies was rated as medium risk of bias.  The findings from the review highlight that the evidence on the impact of Outreach on patient outcomes is inconclusive and contradictory.   It is suggested that further research to explore the processes and mechanisms which hinder or facilitate the implementation of complex healthcare interventions in clinical practice is required.