Background: The extent to which treatment with amlodipine/losartan may help patients and their doctors from Andean countries to reach their treatment goals remains unknown. Methods: We conducted a quasi-experimental, validation study in which patients with primary, uncomplicated hypertension received open-label, fixed combination therapy with amlodipine/losartan 5/50 mg or 5/100 mg according to their baseline blood pressure (BP). The primary outcome was echocardiographic reduction of left ventricular mass (LMV) after 6 months of treatment. Secondary outcomes were changes in BP, uricemia and albuminuria from baseline. We defined patients with adequately controlled hypertension as those with decreases in at least three out of these four variables. Results: From 109 eligible patients with hypertension, 99 started the protocol (70 under the low-dose combination). Echocardiography indices had mutual correlation and contributed independently to the primary outcome (Cronbach’s α index = 0.66). Intention-to-treat analysis showed that 60 patients [60.6%, 95% confidence interval (CI) 50.3–70.3] had reduced LVM. Echocardiographic changes were not associated with dose levels. Favorable changes in BP, uricemia and microabuminuria were seen in 77, 64 and 76 patients respectively. After 6 months there were 64 (95% CI 54–74%) patients with adequately controlled hypertension. Conclusion: Every two of three patients of this sample of Andean countries reached adequate control after 6 months of combined antihypertensive treatment with amlodipine/losartan.