Drug therapy for essential hypertension is now firmly established. Agents presently available, if used wisely, are capable of controlling hypertension in almost every patient requiring such treatment. There are certain important factors which must be carefully evaluated before patients are started on long‐term antihypertensive therapy. Since these factors in large measure determine the value and predicate the success of any drug therapy program, it is essential that they be thoroughly explored and understood at the outset.