Objectives During the last decade, evidence-based medicine has given rise to an increasing number of medical practice guidelines and protocols. However, the work done on developing and distributing protocols outweighs the efforts on guar-anteeing their quality. Indeed, anomalies like ambiguity and incompleteness are frequent in medical protocols. Recent efforts have tried to address the problem of protocol improvement, but they are not sufficient since they rely on informal pro-cesses and notations. Our objective is to improve the quality of medical protocols. ∗ This work has been done in the framework of the EU project Protocure (IST-2001-33049 – Protocure, Improving medical protocols by formal methods).