BACKGROUND: To obtain reference values for the ambulatory blood pressure, 30 normotensive Korean young males, aged 22-28 years(mean age: 25 years) were investigated. METHODS: The ambulatory blood pressure was recorded with SpaceLabs Model 90207 monitor over 24 hours at 20 minutes intervals during day-time(6 am-10pm) and at 30 minutes intervals during night-time (10 pm-6 am). RESULTS: The ambulatory blood pressure of the 30 subjects averaged 119/74mmHg over 24 hours, 122/78 mmHg during day-time and 112/68 mmHg during night-time. The upper limit of normal ambulatory blood pressure was suggested as the value of mean+/-2SD which revealed 131/84mmHg for 24 hours, 134/90 mmHg for day-time and 126/80 mmHg for night-time. CONCLUSION: Reference values for the ambulatory blood pressure, in normotensive Korean young men, were obtained by SpaceLab model 90207 monitor.