BACKGROUND: Peak expiratory flow (PEF) provides a simple, quantitative, and reproducible measure of the existence and severity of airflow obstructions. Peak flow meters are designed to monitor the condition asthma patients. There are many reports showing the normal predicted value of PEF in other countries. studies on healthy Korean adults have been performed in a relatively small sample number and a lower limit for the normal value was not reported. therefore, an attempt to provide normal predictive PEF value with a lower limit was made. METHOD: The PEF(Mini-Wright peak Flow Meter) measurements and spirometry were done in 233 men and 631 woman without history of respiratory disease. all subjects were non-smokers with no respiratory symptoms. the normal predictive value and its lower limit were developed by multiple regression analysis. The result was compared with regression equations in other reports. RESULTS: The regression equation for the normal PEF predictive value(L/min) is 25.117+4.587×Age(year)-0.064×Age2+2.931×Height(cm) in men in men(R2=0.25), and 146.942-0.011×Age2+1.795×Height(cm)+0.836×Weight (kg) in women(R2=0.21). The regression equation for the lower limit of this value (L/min) is 25.117+4.587×Age(year)-0.064×Age2+1.936×Height (cm) in men, and 146.942-0.011×Age2+1.232× Height (cm)+0.481×Weight (kg) in women. The residuals were normally distributed. The PEF in Korean males was similar to those reported in British and Japanese subjects. The PEF in Korean females was similar to that in British subjects, But higher than the PEF in Japanese subjects. The lower limit of normal value was 71% of normal predictive PEF value in men and 76% in women. CONCLUSION: The normal predictive PEF value and its lower limit was measured from 233 male and 631 female asymptomatic, lifelong non-smoking participants. The normal predictive value was different from those of other studies on Korean subjects. Therefore, further studies are required.