Twelve patients admitted to hospital with an acute attack of bronchial asthma were studied. Six were treated initially with nebulized salbutamol solution by inhalation and 1 hour later by ipratropium bromide given in the same way; the other six were treated first with ipratropium bromide and 1 hour later by salbutamol. Ipratropium bromide was shown to be as effective as salbutamol when used as the initial bronchodilator but salbutamol produced significant further improvement when given 1 hour after ipratropium.