We measured growth hormone (GH) concentrations in first morning urine samples in 110 prepubertal children to determine whether asthma therapies affected GH secretion. The children with asthma were assigned to two groups depending on their asthma treatments: 1) 16 children with a history of asthma, currently not on any treatment; and 2) asthmatics taking inhaled corticosteroids (n = 37), short-term oral corticosteroids (n = 15), or long-term non-corticosteroidal therapies (n = 19). Results obtained from these children were compared with a control group of healthy prepubertal children (n = 23) without previous or current symptoms of asthma. Five consecutive urine samples were collected from each child, and GH concentrations (corrected for urine creatinine) were determined by an enzyme immunoassay. The mean ( 5 SD) urine GH concentration determined in the control group (23 healthy prepubertal children) was 15.6 ? 8.7 ng/L (1.88 5 1.29 ng GH/mmol creatinine). The mean (? SD) urine GH concentrations in overnight samples were similar in untreated asthmatics (14.1 5 6.1 ng/L) and in the treatment groups (14.1 ? 7.7 ng/L, inhaled corticosteroids; 16.5 5 11.7 ng/L, oral corticosteroids; 15.9 2 9.8 ng/L, long-term non-corticosteroidal therapies). Irrespective of the manner of expression of urine GH (ng/L) or after correction for urine creatinine concentration (ng GH/mmol), no significant differences were found in the GH excretion among any of the groups. In this study, the intra-individual coefficient of variation for urine GH, expressed as ng/L, ranged between 11 and 87% (median, 32%). When the urine GH was expressed as ng GH/mmol creatinine, the coefficient of variation ranged between 12 and 92% (median, %yo), accounting for approximately 60% of the inter-individual coefficient of variation (mean CV, 56%) and 47% when the urine GH is expressed as ng GHlmmol creatinine. We were unable to determine any short-term differences in urine GH excretion between non-asthmatic children and asthmatics treated with inhaled corticosteroids, oral corticosteroids, or bronchodilators. Our results suggest that there is not an adverse effect of current corticosteroid therapies for childhood asthma on GH secretion.