OBJECTIVES: determinate the factor structure of the Beliefs about Medicines Questionnaire (BMQ) and examine the association of medication beliefs with medication adherence METHODS: Seventeen patients who used antihypertensive drugs participated in semi-standardized interviews. Interviews were recorded and reviewed by two investigators. The medication adherence was measured using the method of count of tablets. An exploratory factor analysis was performed .Multiple linear regression was used to determine whether beliefs about medications were significantly associated with medication adherence RESULTS: Factor analysis resulted in a two solution, explaining 46.7% of cumulative variance among respondents. The factors were labeled: Overuse (Concerns about the way doctors use medications) and Harm (Beliefs that medications are harmful). Chronbach's alpha coefficient was 0.71. Beliefs about medications (Overuse and Harm) were significantly associated with non-adherence to antihypertensive drugs CONCLUSIONS: The factorial structure of BMQ was similar than previously reported in other medical conditions. Also these findings suggest that in addition to telling patients how to take their medications, primary care physicians should educate patients about short and long-term effects of the medication and all possible therapeutic alternatives to improve the adherence to antihypertensive medication