OBJECTIVE To determine compliance, factors affecting compliance to antihypertensive therapy and to compare compliant and non-compliant groups, in a tertiary care setting. METHODS Analytical (cross-sectional) study. METHODS The outpatient clinics at the Aga Khan University from May 2004 to February 2005. METHODS Two hundred patients presenting to the outpatients clinic were included. All patients 18 years and above, who had stage 1 and 2 hypertension, had one clinic visit to a medicine clinic, 6 months prior to presentation and started on antihypertensive medicines, were included. RESULTS Sixty six percent were males and 33.5 % were females. Mean age was 58.1(+/-12) years and mean duration of hypertension was 7.2 (+/- 6.7) years. Fifty-seven percent were compliant and 43 % were noncompliant. In the noncompliant group, 53.4 % had mild noncompliance, 24.4 % had severe non-compliance, while 22% had moderate noncompliance. Factors of noncompliance were 56.8% missed doses due to forgetfulness, 12.7% deliberately missed their doses, 11.6% could not take the medicine due to side effects, 10.4% did not take the dose due to increased number of tablets, 4.6% were not properly counseled by the physician and 3.48% did not take medicines due to cost issues. The mean systolic blood pressure was 126 +/- 19.2 mmHg in the compliant group while it was 133 +/-16.5 mmHg in the noncompliant group p-value 0.004). The mean diastolic blood pressure in the compliant group was 76 +/- 11.9 mmHg, while in the noncompliant group it was 81.9 +/-10.9 mmHg (p-value 0.001). CONCLUSIONS Compliance to antihypertensive therapy in a tertiary care center is significantly good. Forgetfulness was the major reason for noncompliance. The mean blood pressure control was better in the compliant group.