The antihypertensive efficacy and tolerability of losartan/hydrochlorothiazide (HCTZ) and losartan monotherapy as initial treatment were compared in a double-blind trial in Chinese patients with mild to moderate essential hypertension. Patients were randomised to initial treatment with either losartan/HCTZ (50 mg/12.5 mg) or losartan alone (50 mg). The doses were doubled after four weeks if diastolic blood pressure (SiDBP)was >90 mmHg. Both losartan/HCTZ and losartan alone significantly reduced SiDBP and SiSBP from baseline at the first measurement at 4 weeks (-10.1/-15.3 and -6.1/-6.9 mmHg, respectively; p<0.001) and at 8 weeks (-13.1/-18.5 and -8.7/-10.9 mmHg; p<0.001). The reductions with losartan/HCTZ were significantly greater than with losartan alone at weeks 4 and 8 (p<0.001). Both regimens were similarly well tolerated. In conclusion, initial therapy with losartan/HCTZ is effective and well tolerated in the treatment of Chinese patients with mild to moderate essential hypertension and produces a greater reduction in blood pressure than losartan alone.