We measured plasma salbutamol concentrations in 35 children with acute asthma attacks before and after nebulizer therapy. The main finding was that older children had higher concentrations than younger children, despite similar dosage regimens. There was no influence of severity of the asthma attack on the following measures: pre- and post-nebulizer concentrations, absolute and percentage change in salbutamol levels with therapy. We conclude that the theoretical risks of high concentrations in young children were not found and we suggest that the very young may indeed require higher doses due to possible problems in nebulizer technique or differences in kinetics.