Objective:To determine types and frequency of side effects of antihypertensive drugs in patients with diabetes mellitus (DM) type 2 and hypertension.Subjects and Methods:We performed a prospective study of 79 patients with DM type 2 and hypertension, randomly selected by systematic sampling, who were followed over a period of six months. Patients were assessed at baseline and once a month measuring following parameters: types of used antihypertensive drugs and frequency of side effects, the values (mmHg) of systolic (SBP) and diastolic blood pressure (DBP).Results:Out of 79 patients, 48/79 (60.8%) were males and 31/79 (39.2%) were females. The median age in males was 53 years (IQR=48 to 55 years), in females was 53 years (IQR=49 to 56 years). There was no statistically significant difference in median age between males and females (P=0.368). There is a statistically significant difference in the values of SBP [χ2(5)=312.296, P<0.001] and DBP [χ2(5)=216.051, P<0.001] over a period of six months follow-up. The drug side effects were noted in 9/79 (11.4%) patients between 1-2 months, in 6/79 (7.6%) between 2-3 months, in 1/79 (1,3%) between 3-4 months. The most common side effect was cough (11/79 or 13.9%) associated with the combination of ACE inhibitor and thiazide diuretics. In 5/79 (6.3%) patients there were reports of: flushing, palpitations, headache, dizziness and leg edema associated with Ca blockers.Conclusion:The most common side effect of antihypertensive treatment was cough (13.9%) associated with the combination of ACE inhibitor and thiazide diuretic.