Background: Although several risk factors for asthma have been identified in infants and young children with recurrent wheeze, the relevance of assessing lung function in this group remains unclear. Whether lung function is reduced during the first 2 years in recurrently wheezy children, with and without clinical risk factors for developing subsequent asthma (ie, parental asthma, personal history of allergic rhinitis, wheezing without colds and/or eosinophil level >4%) compared with healthy controls was assessed in this study. Methods: Forced expiratory flows and volumes in steroid naive young children with >= 3 episodes of physician confirmed wheeze and healthy controls, aged 8-20 months, were measured using the tidal and raised volume rapid thoracoabdominal compression manoeuvres. Results: Technically acceptable results were obtained in 50 wheezy children and 30 controls using tidal rapid thoracoabdominal compression, and 44 wheezy children and 29 controls with the raised volume technique. After adjustment for sex, age, body length at test and maternal smoking, significant reductions in z scores for forced expiratory volume at 0.5 s (mean difference (95% CI) -1.0 (-1.5 to -0.5)), forced expired flow after 75% forced vital capacity (FVC) has been exhaled (FEF25) (-0.6 (-1.0 to -0.2)) and average forced expired flow over the mid 50% of FVC (FEF25-75) (-0.8 (-1.2 to -0.4)) were observed in those with recurrent wheeze compared with controls. Wheezy children with risk factors for asthma (n= 15) had significantly lower z scores for FVC (-0.7 (-1.4 to -0.04)) and FEF25-75 (20.6 (-1.2 to -0.1)) than those without such risk factors (n= 29). Conclusions: Compared with healthy controls, airway function is reduced in young children with recurrent wheeze, particularly those at risk for subsequent asthma. These findings provide further evidence for associations between clinical risk factors and impaired respiratory function in early life.