The importance of systematic reviews of diagnostic and screening tests has grown significantly in recent years as technological advances are making a vast array of such modalities available to the clinician. The information from such systematic reviews is necessary for defining the proper and efficacious use of diagnostic and screening tests in the clinical setting; for making decisions about health care policy and financing; and for assessing diagnostic technology in order to determine areas for further development and evaluation. Ultimately, the results of the systematic reviews will help health professionals and consumers choose among available alternative tests and correctly interpret test results. The Cochrane Collaboration is an international organization that aims to help people make well-informed decisions about health care by preparing, maintaining and promoting the accessibility of systematic reviews. The Cochrane Library is well known source of high quality comprehensive reviews of the effects of health care interventions. However, systematic reviews of the accuracy of diagnostic tests are not yet included in the Cochrane Library. To rectify this situation the Collaboration decided to initiate the development of a Cochrane Database of Reviews of Diagnostic Test Accuracy, which in time will be published as a separate database within the Cochrane Library. A working group was formed in September 2003 to develop the Handbook and software for the Cochrane Diagnostic Reviews (CDR). The group has worked extensively in the past two years, via in-person meetings and the internet, and has developed a draft of the Handbook. Further work is needed to complete the Handbook and to finalize the specifications for the accompanying software. In particular, further discussion and development is needed for the crucial chapters on methods and on the interpretation of systematic reviews. To complete the development of the CDR Handbook a Workshop is proposed to be held in September 2006. Participants in the Workshop will be members of the CDR working group. The completed Handbook will not only enable the conduct of Cochrane Diagnostic Reviews but will also provide guidance to all researchers involved in systematic reviews of diagnostic and screening tests.