Children of atopic parents are recognised as being at higher risk of developing bronchial asthma, drawing the attention of prevention strategies towards this population. Due to recent advances, lung function abnormalities in asthmatic children may now be measured early in life. The aim ofthis investigation was to examine possible predictors of lung function development in a sub sample of high-risk infants who took part in an allergy avoidance study In 60 babies of atopic parents, measurements of upper airways inflammation were performed at 4 weeks of age, respiratory symptoms were assessed at 6 and 12 months of age, and lung function (Vmax, FRC) was measured at 18 months by the rapid thoracoabdominal compression technique. Twenty-eight babies were enrolled in an allergen avoidance program, and 32 recruited as controls. No significant differences were detected for V'max,FRC between the intervention group (mean 331 ml s(-1)) and the control group (359 ml s(-1)), P = 0.382. A multiple linear regression model could explain levels of V'max FRC by weight gain since birth (beta = -35.35 ml s(-1) kg(-1), P = 0.022) and by eosinophilic cationic protein (ECP) (beta = -0.95 ml s(-1) microl(-1), P = 0.044), but not by intervention. Lung function measured at the age of 18 months in high-risk children is associated with weight gain and nasal ECF.