1. The hypotensive effect of methyldopa alone or associated with other hypotensive drugs was evaluated in 155 patients. After 10 days of treatment, the blood pressure was back to normal in 80% and in 50% of the patients with mild and moderate hypertension, and it was significantly decreased in those with severe hypertension. 2. Contrary to other hypotensive drugs, it did not produce a significant increase in BUN and serum creatinine. Occasional or recurrent episodes of orthostatic hypotension were observed in about 18% of the cases, but in none did it produce important symptoms of cerebral or myocardial ischaemia.