As part of a larger effort to automate guidelines we determined the number and types of clinical variables required to implement two complex clinical guidelines and the adequacy of the electronic medical record (EMR) to capture them. 178 unique variables were required by both guidelines. Variables were classified as simple (existing observation terms in the EMR), calculated (transformations of simple variables), and complex (requiring multiple simple variables and logical rules for combining them). Many variables are unlikely to be instantiated in an EMR without focused efforts to collect them. In addition, many variables required knowledge that was neither provided in the guideline nor referenced. We conclude that, although the EMR contains the necessary variables to implement these guidelines, successful automated implementation requires unambiguous definition of required terms, incorporation of additional knowledge not provided in the guideline and modification of workflow to collect variables not normally captured in routine clinical care.