BACKGROUND: Simple renal cyst is the most common cystic deformation found in adults. However, there were a few systematic Korean reports for the clinical symptoms and complications of simple renal cysts. The author's purpose was to determine the relationship between simple renal cysts diagnosed by abdominal ultrasonography and hypertension. METHODS: Among 13,482 persons who took a routine physical examination at Ulsan University Hospital in 2002, 5,127 persons who took medical examinations again in 2010 were selected. We excluded persons who had renal cyst, hypertension, diabetes, liver cirrhosis, kidney disease, thyroid disease, and cancer in 2002. Analysis was conducted for 505 subjects with newly diagnosed simple renal cyst and 2,744 subjects without renal cyst in 2010. The simple renal cyst group was compared to a control group without renal cyst. RESULTS: Among 3,249 subjects, simple renal cyst and hypertension were newly diagnosed in 505 subjects and 503 subjects. The subjects who had simple renal cysts had significantly higher hypertension incidence (odds ratio [OR], 1.53; 95% confidence interval [CI], 1.20 to 1.94). Significant hypertension incidence was observed especially when the subjects had cysts located on both kidneys (OR, 3.48; 95% CI, 2.12 to 5.71), two (OR, 3.08; 95% CI, 1.84 to 5.15) or more cysts (OR, 3.12; 95% CI, 1.38 to 7.04), and larger cysts more than 1 cm in diameter (OR, 1.55; 95% CI, 1.16 to 2.07). CONCLUSION: The presence of simple renal cysts was significantly positively related to the incidence of hypertension. Bilateral distribution, two or more number, and larger size than 1 cm diameter were the characteristics of simple renal cyst related to hypertension.