Background: The Dutch College of General Practitioners (NHG) is the scientific association of Dutch GPs. One of its tasks is to develop, disseminate and implement clinical practice guidelines to support evidence-based decision making by GPs. One of the structural parts of the guideline development process is to search for randomised controlled trials and systematic reviews in databases such as MEDLINE and The Cochrane Library. Objective: To determine to what extent Cochrane reviews are used to underpin recommendations in NHG guidelines and why they are either included or excluded. Methods: First, all NHG guidelines published in 2006 and 2007 were checked for the number of Cochrane references. Second, we performed a search in the Cochrane Database of Systematic Reviews taking into account the closing date of the literature search for each guideline. Finally, we interviewed 12 (of 14) NHG staff members responsible for the development of the 20 guidelines in order to collect their experiences and considerations for including or excluding Cochrane reviews. Results: Twenty guidelines included a mean number of 109 references (SD 53) of which six were Cochrane reviews (SD 8). On average, 43% of the available Cochrane reviews were included in the guidelines. We found a strong correlation between the number of Cochrane reviews mentioned in a guideline and the number of available reviews in The Cochrane Library (R2 = 0.78). The interviews showed that an important reason for excluding available Cochrane reviews was the lack of relevance for a specific guideline. However, all of the interviewees had a positive overall opinion on the usefulness of Cochrane reviews and The Cochrane Library for guideline development. Opinions differed slightly on the perceived level of evidence and the user-friendliness. Conclusions: Approximately half of the available Cochrane reviews were used in NHG guidelines. The chance of Cochrane reviews being included in these guidelines correlates positively with the number of available reviews. Guideline developers are very pleased with Cochrane reviews and are willing to incorporate them if relevant. However, the availability and relevance for primary care varies. The Cochrane Primary Health Care Field may help increase the relevance of Cochrane reviews for general practice.