In the evaluation and management of bronchial asthma, simple instruments for measurement of peak expiratory flow rate (PEFR) are needed. There are two main reasons for a population study of a variable such as PEFR. The first is to establish a reference range for clinical use and the second is to examine population differences or the physiological development of the variable. Normal values for Turkish children have not been published. In a cross sectional study, we measured PEFR in 2791 healthy school children (1468 boys and 1323 girls) aged 7-14 years, living in 6 different regions of Istanbul, the largest and cosmopolitan city of Turkey. We used the Mini Wright peak flow meter which is a practical and common way of measuring PEFR. All tests were performed in the standing position with a nose clip with the best of three trials recorded. We found that height, age and sex had a significant effect on the regression equation. The equation for prediction of PEFR in boys was calculated as (3.5 x height) + (9.2 x age) - 256.5 (p<0.0001, r=0.83), and for girls (3.3 x height) + (10.2 x age) - 263.7 (p<0.0001, r=0.81). These findings will serve as an important basis for preparing charts for normal PEFR values for Turkish children. © 1997 Wiley-Liss, Inc.