Since the early nineties, the peak expiratory flow (PFE) has been included in consensus recommendations on control and treatment of asthma. Due to the fact that the PFE presents with variations in different populations, the values for PFE were determined in healthy Uruguayan children. Three hundred and sixty two boys and 437 girls from 9 different schools, without prior history of respiratory disease, use of respiratory PFE were determined using a Vitalograph flowmeter in standing position, and the highest value of 3 or more procedures was recorded. The children were studied grouped by gender and in weight intervals of 5 kg, length intervals of 10 cm and age intervals of 1 year. The percentile 10, 50 and 90 were determined for each class interval and was correlated with a 2nd degree polinomial function. The correlation coefficient (r2) for percentiles 10, 50 and 90 was of 0,99, 0,98, and 1,00 in the case of length, being a little less in case of age and weight. The values of PFE were greater for boys in comparison to girls from 40 kg onwards, an age of 9 years and length of 140 cm. The values obtained in this study were compared with those previously published