Background: The interdisciplinary nature of public health makes identifying studies for systematic reviews a much more complex process than that for reviews in clinical medicine. Having just completed a particularly complicated review of public health interventions, we will consider whether it was necessary or valid to search as many sources as we did. Objectives: To identify and compare information sources and to assess their contribution to papers reviewed in full text and to those which were included in the review. To establish whether the included papers were all retrieved in the exhaustive literature search. Methods: A literature search was conducted in 25 databases using a comprehensive list of search terms. In addition, a range of snowballing methods was used. We will examine the full text papers identified from each source, including those that were unique to that source. Results: The comparison will identify the sources that contributed potential and actual papers for the review. Conclusions: The findings will have implications for those developing search protocols and will contribute to the guidance available to authors embarking on systematic reviews of public health interventions.