We investigated the bronchodilating effect of intravenous MgSO4 in acute severe bronchial asthma. Infusion of MgSO4 caused a significant improvement in FEV1 (0.94 +/- 0.39L to 1.3 +/- 0.44 L) and an improvement in clinical signs and symptoms in ten out of 12 administrations. The bronchodilating effect of MgSO4, however, was significantly less than that of subsequent albuterol inhalation (FEV1 improvement from 1.13 +/- 0.41 L to 1.72 +/- 0.49 L). These findings confirm that intravenous MgSO4 may be used as an adjunct to classic beta 2-agonist therapy in cases of severe acute asthma; its exact place in the treatment of asthma remains to be determined in large-scale studies.