Most hypertensive patients need more than one drug to reach recommended blood-pressure targets. We investigated the effects on 24-h ambulatory blood pressure (ABP) of the angiotensin-receptor blocker, valsartan, in combination with hydrochlorothiazide (HCTZ), compared with the calcium-channel blocker amlodipine in a Brazilian population in a multicentre, double-blind, double-dummy, parallel group, controlled study in 373 patients with essential hypertension. After a 2-week washout period, patients with a mean sitting systolic blood pressure (SBP) of 160-190 mmHg were randomized to receive either valsartan 160 mg o.d., or amlodipine 5 mg o.d. for 2 weeks and subsequently force-titrated to valsartan 160 mg/HCTZ 25 mg o.d. or amlodipine 10 mg o.d. This regimen was continued until the end of the study at week 8. The primary efficacy parameter was the change from baseline to week 8 in mean 24-h SBP. Secondary endpoints were change in mean 24-h diastolic blood pressure (DBP), tolerability and safety of treatments. Valsartan/HCTZ achieved a mean reduction in systolic ABP of -19.1 +/- 11.3 mmHg compared with -20.7 +/- 12.0 mmHg with amlodipine (p = 0.324 for the comparison) and in diastolic ABP by -11.1 +/- 7.4 mmHg vs -11.6 +/- 7.2 mmHg by amlodipine (p = 0.853 for the comparison). The valsartan/HCTZ group exhibited markedly lower rates of adverse events and discontinuations than the amlodipine group. Peripheral oedemas were far more frequent with amlodipine than with valsartan/ HCTZ (1.6% with valsartan/HCTZ; 16.8% with amlodipine). Thus, the valsartan 160 mg/HCTZ 25 mg combination appears to be as efficacious as amlodipine 10 mg in this patient population but better tolerated.