Despite availability of effective antihypertensives, blood pressure (BP) control is usually inadequate. The Reasons for not Intensifying Antihypertensive Treatment (RIAT) registry evaluated the reasons behind not modifying treatment in an international, cross-sectional study in 16 countries. Methods and results: The Taiwanese cohort of RIAT consisted of 8922 patients with untreated/uncontrolled essential hypertension recruited from 22 centers in the country. At the first visit, physicians selected target BP and antihypertensive treatment, and at the next three visits they measured BP and modified treatment/provided justification for not modifying treatment. Mean target BP selected by physicians was 134.6/84.6 ± 5.1/5.0 mmHg, respectively. Patients’ individual risk stratification determined the BP goals. More patients achieved targets according to the physicians’ opinion than based on actual BP measurements: visit 2–50.6% vs. 48.6%; visit 3–58.4% vs. 55.2%; and visit 4–61.2% vs. 57.0%. At each visit, treatment remained unchanged for >60% patients not reaching target; the most common reason for this at visit 2 was the assumption that the time was too short to assess new drug therapy and at visits 3 and 4 was the assumption that target was reached/had almost been reached. Conclusion: About 40% Taiwanese hypertensive patients in RIAT did not reach BP targets after an average of 4 months’ follow-up. The most common reason for not modifying treatment was the assumption that the target had been reached or had almost been reached.