Objectives: As in software product lifecycle, the effort spent in maintaining medical knowl edge in guidelines can be reduced, if modularization, formalization and tracking of domain knowledge are employed across the guideline development phases. Methods: We propose to exploit and combine knowledge templates with medical background knowledge from existing thesauri in order to produce reusable building blocks used in guideline development. These tem- plates enable easier guideline formalization, by describing how chunks of medical knowledge can be combined into more complex ones and how they are linked to a textual representation. Results: By linking our ontology used in guideline formalization with existing thesauri, we can use compilations of thesauri knowledge as building blocks for modeling and maintaining the content of a medical guideline. Conclusions: Our paper investigates whether medical knowledge acquired from several medical thesauri can be molded on a guideline pattern, such that it supports building of executable models of guidelines. © 2009 Schattauer.