The safety of using inhaled beclomethasone dipropionate for the treatment of severe asthma during pregnancy was evaluated during 45 pregnancies in 40 women. Despite chronic administration of theophylline and, in some women, ephedrine, the asthma was so severe that corticosteroids were essential to prevent emergency room visits and status asthmaticus. At conception, beclomethasone dipropionate was being used regularly during 38 pregnancies and was initiated during the first trimester in 4 other pregnancies. The range of beclomethasone dipropionate inhalations was 4 to 16/d with a mean of 9.5/d (336 micrograms). Prednisone administration was necessary during 37 pregnancies. Status asthmaticus occurred in five women but no mothers or fetuses died. Cardiac malformations occurred in an infant born to a woman who was diabetic and schizophrenic whose pregnancy was complicated by diabetic ketoacidosis and status asthmaticus. It is not known whether beclomethasone dipropionate was the cause of these malformations. The prevalence of congenital malformations (1 of 43 live births) is within the normal range and shows that treatment with beclomethasone dipropionate is safe during pregnancy when recommended doses are used.