PURPOSE: This study was implemented to investigate the prevalence of proteinuria and its combined morbidity in apparently normal adults. METHODS: We examined the mass screening data of Health Promotion Center in Seoul National University Hospital from May 1, 1995 to February 11, 2000. The random urine samples of all screenees were examined by dipstick test. Among them 22,595 adults(men 11,737 and women 10,858) who didn't take anti- hypertensive medication and whose fasting blood sugar <126 mg/dL were included in this analysis. RESULTS: The prevalence of proteinuria was 6.7% in men and 3.6% in women. Risk factors for proteinuria by simple correlation analysis were age, sex, body weight, systolic blood pressure, diastolic blood pressure, fasting blood sugar, blood urea nitrogen, serum creatinine, total cholesterol and smoking. As the degree of proteinuria increased, the systolic and diastolic blood pressures also increased significantly and creatinine clearance significantly decreased above the '++' level of proteinuria. Probability of proteinuria was calculated at each blood pressure level graded by JNC VI. With the increase of the level of blood pressure, the probability of proteinuria increased significantly between normal and high normal, high normal and hypertension1, and hypertension 2 and hypertension 3 level. Creatinine clearance and blood pressure level showed negative correlation. When total screenees were divided to proteinuria and no proteinuria groups, proteinuria group showed significant decrease of creatinine clearance in high normal and hypertension 1 level. CONCLUSION: Our results suggest that proteinuria in the apparently normal adults is not a benign condition, and it can be accompanied by significantly increased blood pressures and decreased renal function.