Background: Valsartan is an angiotensin AT1 receptor antagonist. Clinical studies have shown that this is an effective and well tolerated drug. Aim: To compare valsartan with other commonly used antihypertensives in a National multicentric study. Material and methods: Between 1997 and 1998, a pharmacological surveillance of patients with mild or moderate hypertension, coming from different regions of the country, was carried out. Patients were followed during 8 weeks. In the group treated with valsartan, the initial dose was 80 mg/day. After four weeks of therapy, and according to patient's response the dose of valsartan or of the other antihypertensives was modified. Results: Five hundred ninety three patients, aged 59 years old as a mean, were included in the study. Of these 434 (265 female) received valsartan and 159 (101 female) other antihypertensive drugs. Fifteen percent of patients treated with valsartan and 25% of patients with other medications required a dose change at four weeks, due to lack of response (p < 0.01). At week eight, 1.5% of patients with valsartan and 17.4% of patients with other medications reported adverse effects such as cough, headache, edema or flushing (p < 0.01). Conclusions: In this Chilean observational multicentric study, valsartan proved to be more effective and to cause less adverse effects than commonly used medications in hypertensive patients. (Rev Méd Chile 2000; 128: 475-82)