Introduction: Isolated systolic hypertension (ISH) happens when diastolic blood pressure is less than 90mmHg and systolic blood pressure is 140mmHg or higher. ISH is the most common form of high blood pressure in people older than age 65. Background: In the elderly, the aorta is rigid and PWV is high, so reflective pressure waves return early and occur in the systolic period, reducing coronary perfusion, and adding systolic blood pressure, which is called augmentation index (AI). Increases in systolic blood pressure cause cardiac hypertrophy and heart failure, and decreases in diastolic blood pressure cause ischemic heart disease. Aging results in a continuous increase in sBP while a plateau of dBP occurs at the age of 50–60 years, followed by a decrease. ISH is classified into 2 types, depending on the pre existence of essential HTN (E-HTN). If a patient had E-HTN and then dBP decreased during aging, it is considered as the “burned-out type.” On the other hand, if there was no prior E-HTN and sBP increased while dBP decreased due to an aging-induced increase in stiffness of the large arteries, it is called “de novo ISH”. The European Society of Cardiology and European Society of Hypertension (ESC/ESH) 2018 guidelines for hypertension (HTN) are helpful because they recommend a lower safety cut-off for in-treatment dBP. To prevent tissue hypoperfusion, these guidelines recommend that dBP should be ≥70 mm Hg during treatment. Method and Results: We encounter many ISH patients at the clinical site, especially with dBP already below 70mmHg. (ex. 150/69mmHg , 160/64mmHg, 180/68mmHg) Most of these patients are elderly and are taking several types of antihypertensive drugs. Since most existing antihypertensive drugs lower systolic and diastolic blood pressure together, they are not suitable for use to ISH patients as above. (ex. ACE inhibitors 12.5/9.5mmHg↓, Calcium channel blockers 15.3/10.5mmHg↓, Thiazide diuretics 15.3/9.8mmHg↓) We often use BCD101 to treat ISH patients, and more selectively lower systolic blood pressure while maintaining diastolic blood pressure. Conclusions: Our aim was to raise awareness about the problem of treating ISH patients with dBP that is too low. Considering guidelines recommend that DBP should be ≥70mmHg during treatment, it is important and urgent to develop appropriate antihypertensive drugs for patients with ISH.