Twenty subjects (aged 6-20 years) with moderately severe bronchial asthma participated in an open controlled trial with intravenous immunoglobulin (IVIG) given as five monthly infusions with a mean dose of 0.8 g/kg body weight. A follow-up was performed 4 and 14 months after the treatment period. Nine of 14 children in the treatment group completed the trial. Two children experienced severe headache after the first infusion, another two patients were taken off the study for reasons unrelated to the IVIG therapy, and one patient dropped out from lack of motivation. In six of the IVIG-treated children, there was a reduction in the daily intake of inhaled steroids at an unchanged or reduced histamine reactivity. Of the remaining three children, two showed a reduction in bronchial hyperreactivity, but their steroid dose was not reduced. Six patients participated in a reference group to determine seasonal variations of symptoms. One of them improved during the study period, and the condition of the other five deteriorated, as indicated by increased medication without reduced histamine reactivity. After 14 months, there were no significant differences in clinical symptoms, nor in sensitivity to histamine between the treated patients and the controls, as the condition had improved also in the latter. We have thus been able to confirm, in a group larger than those in previously published reports, some clinical improvement of asthma by IVIG therapy at a lower dose than previously used and in children with only moderately severe disease. The effect was still present 4 months after the termination of IVIG therapy but not after 14 months.(ABSTRACT TRUNCATED AT 250 WORDS)