Peak expiratory flow rate was estimated in 569 school children in Ibadan to determine normal values in Nigerians. Two hundred and seventy-six boys and 293 girls, aged 6-18 without antecedent history of respiratory disease, from different socio-economic backgrounds were selected. The peak expiratory flow rate (PFR) was estimated using the Wright peak flowmeter. The results indicated that the mean values of Nigerian children were lower than those of Caucasians of the same height, sex and age. The possible reasons for this are discussed. The PFR values were found to correlate highly (P less than 0.01) with age, weight and height, and also with FVC and FEV1. In this study, PFR correlated more closely with weight than height, contrary to the results observed in Caucasian children. Since there is a positive correlation between PFR and FVC or FEV1, PFR can therefore be used in assessment of respiratory function in clinical practice, particularly in younger children, who cannot adequately cooperate when the spirometer is used for lung-function studies.