Respiratory disorders seem to be better tolerated during pregnancy than disorders of the cardiovascular system. Pregnancy seems to have a variable effect on bronchial asthma although respiratory function in general shows little change. Similarly patients with bronchiectasis do not tend to show functional deterioration. Fetal growth, however, may be adversely affected in these conditions if arterial hypoxaemia is present. The problems of drug treatment of respiratory disorders in pregnancy, particularly asthma and tuberculosis, are discussed.