Abstract
A “4S” model for the organisation of evidence-based information services, proposed several years ago,1 begins with original studies at the foundation; syntheses (that is, systematic reviews, such as Cochrane Reviews) at the next level up; then synopses (very brief descriptions of original articles and reviews, such as those that appear in the evidence-based journals); and the most evolved services, systems (such as computerised decision support systems that link individual patient characteristics to pertinent evidence) at the top.