To determine the influence of asthma and its treatment with inhaled corticosteroids on growth, linear growth velocity, and the growth hormone axis in prepubertal children, we performed a longitudinal study for 12 months in 56 children with asthma, aged between 4.4 and 11.7 years. Height, weight, skin-fold thickness, and lung function were measured every 3 months and bone age at entry to and exit from the study. A 24-hour serum growth hormone concentration profile and fasting insulin-like growth factor I levels were measured halfway through the year. Seventy-four percent of boys and 62% of girls had heights below the 50th percentile. Growth velocity in the nonsteroid-treated control group (n = 13) was normal; 10 of 20 children taking beclomethasone grew slowly (14/20 used a dry powder device), and 4 of 19 children taking budesonide grew slowly (15/19 used a spacer). Three of four children using inhaled steroids and prednisolone grew slowly. In none of the treatment groups were measures of growth hormone secretion or levels of radioimmunoassayable serum insulin-like growth factor I affected. We conclude that slow growth in steroid-treated children with asthma does not appear to be associated with major perturbations in the growth hormone axis.