Every year, numerous clinical practice guidelines (CPGs) are published on a same topic. They may be conflicting, thus infringing clinicians' confidence in adhering to them. In order to build a clinical decision support system to assist GPs in the management of hypertension, we have considered three recent CPGs written in French. We developed a methodological framework to evaluate how consistent the three CPGs were. After a manual extraction of recommendation rules, all patient profiles covered by the CPGs have been identified. Then, ontological modeling and reasoning were used to build a subsumption graph of all profiles. This graph allows the retrieval of recommendations that could be conflicting. Results show that if rules are different in the three CPGs according to a document-based approach, many profiles are related through subsumption, and no critical inconsistencies were discovered when implementing an ontological modeling.