Background: The guidelines produced by the Scottish Intercollegiate Guidelines Network (SIGN) are based on a systematic search of the literature. Currently, full coverage of the literature is ensured by searching in multiple databases. As a minimum, a SIGN Information Officer will search in MEDLINE, EMBASE, CINAHL, PsycINFO, The Cochrane Library and a predefined list of websites (e.g. NGC and the TRIP database). However, such an exhaustive approach is very time-consuming, and the value of searching beyond MEDLINE is being questioned. Objectives: This study examined the reference lists from five SIGN guidelines. We determined the number of references that were indexed in MEDLINE, and how many were unique to other sources (i.e. EMBASE, CINAHL, PsycINFO, The Cochrane Library and website search). The contribution of the references from the other sources was considered. Methods: We examined the reference lists from five SIGN guidelines that were published in the last two years: SIGN 90: Diagnosis and management of head and neck cancer; SIGN 91: Bronchiolitis in children; SIGN 92: Management of hepatitis C; SIGN 98: Assessment, diagnosis and clinical interventions for children and young people with autism spectrum disorders; SIGN 99: Management of cervical cancer. PubMed Single Citation Matcher was used to identify the references that were indexed in MEDLINE. The remaining references were searched for in all the other databases. Results: Only the ‘‘Bronchiolitis in children’’ guideline has been evaluated for this study so far. Out of 110 references, 96 were indexed in MEDLINE. Of the remaining 14, 11 were identified from sources other than the five databases (e.g. from search of various websites); one was indexed in both EMBASE and CINAHL; and two were unique to EMBASE. Of the three references indexed in EMBASE and/or CINAHL, only two supported a recommendation. If either of these had been excluded, the recommendations would have been unchanged. Conclusions: For the ‘‘Bronchiolitis in children’’ guideline, there was little value in searching beyond MEDLINE and a predefined list of websites. We are still assessing the other guidelines.