Low adherence to pharmacological treatment in patients diagnosed with hypertension is related to poor blood pressure control and an increased incidence of cardiovascular complications and deaths. A cross-sectional study was performed to determine conditioning factors towards adherence. Questionnaires and clinical evaluations were applied to 187 patients attending three first-level health units; in 130 of them laboratory tests were carried out. Diagnostic criteria were based on the European Clinical Practice Guidelines; adherence was based on the Morinsky test. 57.1% of patients had blood pressure values above the controlled threshold, and 71.1% reported non-adherence to pharmacological prescription. Factors associated whit low adherence were coexisting moderate to severe depression (OR = 2,054; CI 1,064 - 3,964), low educational level (3.75 ± 3.05 years), poor understanding of medical prescriptions (OR = 2.3 CI 1.188 - 4.477), irregular supply and limited economic access to prescribed drugs ((OR = 1.97 CI 1.08 - 3.817), and low satisfaction with the care offered at health services (OR = 2.45; CI 1.202-5.00).