Background: Monitoring of respiratory function is important in the diagnosis and management of respiratory disease. The forced oscillation technique requires minimal patient cooperation and is ideal for the determination of respiratory function in young children. This study aimed to develop reference ranges and to document the repeatability in healthy young children using commercially available forced oscillation equipment.Methods: The forced oscillation technique, which uses a pseudo- random noise forcing signal between 4 and 48 Hz, was used to measure respiratory function in healthy young children. Repeatability over a 15 min period was also assessed. Regression equations and standardised Z scores were determined for respiratory resistance ( Rrs) and reactance ( Xrs) at 6, 8 and 10 Hz.Results: Respiratory function was obtained in 158 healthy children aged two to seven years and between 92 and 127 cm in height. Oscillatory respiratory mechanics exhibited linear relationships with height. Withintest variability for resistance ranged between 6% and 9% and between 17% and 20% for reactance. Resistance and reactance did not change significantly over a 15 min period.Conclusions: Reference ranges for respiratory impedance variables in healthy children aged two to seven years are presented. The short- term repeatability of forced oscillatory variables in this age group is reported, allowing appropriate cut- off values for therapeutic interventions to be defined.