Background: Although evidence has shown the benefits of blood pressure (BP) control and recent development of pharmacological therapeutics, BP control is sufficient in only a small percentage of the hypertensive population. We designed this study to investigate the characteristics, control rate, and factors affecting BP control in hypertensive patients treated by primary physicians in Korea. Methods: The study was a multi-center, nationwide, cross-sectional, population-based survey conducted to identify the current status of hypertension treatment in Korean patients. A direct mail survey was sent to a random sample of 800 primary care clinics across the nation. A total of 529 physicians in 510 clinics agreed to participate in this study (63.8%). Among the recruited 13,452 patients, 13,184 cases were included in the analysis. Results: Among the antihypertensive agents, calcium channel blockers (62.5%) and agent blocking renin-angiotensin systems (ACE inhibitor or ARBs) (60.0%) were most commonly used. Of the included patients, 47% were on combination drug therapy for controlling hypertension. BP was controlled in 6,723 patients (51.0%). However, the control rate was lower in patients with diabetes (21.6%) or chronic kidney disease (19.9%). Furthermore, the mean systolic and diastolic BP were higher in patients with diabetes and/or chronic kidney disease. The mean BP level was higher in patients with combination therapy than with single drug therapy. Male sex, cardiovascular comorbidities, long duration of hypertension, and unhealthy lifestyle were associated with poor control of hypertension. In multivariate analysis, diabetes (OR: 5.567; 95% CI: 5.054-6.133) and chronic kidney disease (OR: 3.396; 95% CI: 2.541-4.539) were the most significant independent factors related to poor BP control. Conclusion: The rate of BP control is still largely unsatisfactory, especially in patients with diabetes and kidney disease, who could benefit the most from effective BP control. However, increasing the knowledge of primary physicians about hypertension guidelines appears to be associated with an improvement in the hypertension control rate, which is related to more aggressive drug treatment.