Background/Aims: This retrospective analysis compared progression-free survival (PFS) in 111 patients who developed or had preexisting hypertension with those who did not during treatment with second-line sunitinib. Secondary objectives included overall survival (OS) and safety. Methods: Patients with metastatic renal cell carcinoma (mRCC) received sunitinib 50 mg orally once daily in 6-week cycles according to a 4-week on/2-week off treatment schedule. Treatment was continued until disease progression, unacceptable toxicity, withdrawal of consent, or death. Resting blood pressure (BP) was monitored by clinic and home measurements. Hypertension was defined as systolic BP ≧140 and/or diastolic BP ≧90 mm Hg. Subsequent antihypertensive treatment was empirical, depending on the patient. Results:Fifty-four (48.6%) patients experienced elevated BP related to sunitinib. Of these, 10 had preexisting hypertension. Patients who developed hypertension related to sunitinib treatment experienced significantly longer PFS and OS compared to those who did not (p < 0.00001). Patients who required at least 3 antihypertensive drugs had the longest PFS (p = 0.00002) and OS (p = 0.00001). Conclusions: The development of hypertension during sunitinib treatment was a positive predictive factor associated with a significantly longer PFS and OS in patients with mRCC.