We compared the structure and content of guidelines for hypertension management across countries to gain an understanding of where differences between them originate from. Four guidelines published between 2003 and 2006 were selected. Two were issued by national agencies in the United Kingdom and France, and two were issued by working groups or national medical societies in the United States and in Europe. The structure of guidelines, the content of each section and their underlying bibliographic references were compared between authoring bodies. If differences were found between guidelines in terms of content, we analysed the rationales. The guidelines were sufficiently similar in structure, showing common sections such as lifestyle interventions, cardiovascular risk assessment and drug therapies. However, contentwise, major differences were observed across the four hypertension guidelines in virtually every section of the document. The definition of hypertension was consistent, whereas the grade stratification was not. Information concerning the blood pressure self-measurement, the estimation of cardiovascular risk and the antihypertensive drugs proposed for initial treatment also varied. Most of the differences were present in both guidelines and their rationales, but some were only found in the guidelines. The bibliographic references for the rationales differed significantly, with only 1.2, 2.2 and 8.8% of the total number of references were common to four, three and two authoring bodies, accounting for the variability. We conclude that improving the selection process of bibliographic references and the extraction process of guidelines from the rationales might be the first step to harmonize guidelines' development.