Sixty-three hypertensive patients were treated with debrisoquin sulfate, a new sympathetic blocking drug, for periods of 6 to 33 months. Good initial blood pressure control was achieved in over 80% of this series, and over 75% maintained good or fair control over the period of the study. At least one-half of the patients required increases in dosage or the addition of a diuretic with the passage of time. Side effects, especially postural dizziness, were not uncommon but seldom necessitated withdrawing the drug. Debrisoquin is an effective and potent antihypertensive agent, and the development of tolerance and side effects have not so far given rise to practical difficulties in blood pressure control.