This study uses grounded theory methodology to generate a substantive theory that describes and explains the problem of high blood pressure control among Iranian patients. High blood pressure control is a major world health problem on which many studies have been carried out. Most of these studies have been done by quantitative research methods. The main purpose of this qualitative research was to determine the essential structure of high blood pressure control in an Iranian hypertensive population and to identify a theoretical explanation for this problem. Four interrelated concepts: ‘non-compliance’, ‘lack of knowledge’, ‘lack of effective caring relationship’, and ‘necessity of partnership’ were identified. Based on these processes, a partnership care theory was developed that provides an appropriate context for the active participation of patients, nurses and physicians in the control of hypertensive disease. This theory can be utilized in the control of hypertension as well as other chronic diseases.