GLIF was published in mid-1998 [1,2] as a specification for machine-readable representation of clinical guidelines and protocols. It resulted from a joint effort of medical informatics researchers from Stanford University, Harvard University (groups at Brigham and Women's Hospital and Massachusetts General Hospital), and Columbia University. Although its publication is fairly recent, the initial specification has been used as a basis for further work by a number of researchers, as well as for the implementation in at least one operational hospital information system environment [3,4]. The need for practice guidelines to reduce costs and variability in health care practice, and ultimately improve patient outcomes cannot be overemphasized. Availability of inexpensive networks of computers in every clinic or private practice in the US is now a reality. Implementation of guidelines in computer-based decision support systems is one of the requirements to disseminate and implement guidelines in medical practice. A machine-readable format for guideline interchange is necessary to allow reuse of encoded guidelines in a variety of institutions, utilizing appropriate software. GLIF is the most comprehensive representation that has been proposed for this purpose. The purposes of this workshop are to: (1) promote discussion of computer-based implementation of practice guidelines; (2) provide practical, science-based information regarding clinical practice guidelines to medical practitioners and to consumers and other health care purchasers (3) enable researchers in the field of computer implementation of guidelines to update themselves about other groups' developments. Towards that end, we will review practical applications of GLIF and related representations, analyze shortcomings, and propose necessary extensions.