Measurement of peak expiratory flow rate (PEFR) is required for effective asthma treatment, but ethnic differences affect the application of prediction equations for lung function. PEFR was measured in a representative sample of 1000 students in Nablus, Palestine. Predicted PEFR equations for Europeans and Iranians were applied to both males and females in age groups < 21 and > or = 21 years. There was a statistically significant correlation between the predicted PEFR values in Palestinians and both equations in both males and females regardless of age. Equations developed on Iranians were more useful for Palestinians than the European equations, but there is a need to develop our own nomograms.