Fourteen patients with acute asthma were randomly distributed between two equally large groups. They received a two-hour intravenous infusion twice a day. Group 1 was treated with corticosteroids and group 2 with corticosteroids and the beta 2-adrenergic agonist terbutaline. The effects of treatment were evaluated by clinical examination and measurement of FEV1 on four consecutive days; in the morning before treatment and then hourly for six hours. The mean FEV1 remained statistically unchanged in group 1. In group 2, mean FEV1 showed a slight but significant improvement on the first day, then a more and more marked increase on the second, third and fourth days. Comparison between the two groups showed that differences in mean FEV1 were significant at the first, second and third hour of the first day and from the first to the sixth hour on the other three days. An additional group of seven patients was treated with beta 2-adrenergic agonist alone. In this group, only a slight increase in FEV1 was noted. This work might suggest an advantage in combining bronchodilators and corticosteroids in the treatment of severe acute asthma.