Thirty-six patients with a combination of reversible and persistent airway obstruction were treated with ipratropium bromide, salbutamol and a combination of both in high dose by nebulizer after a control period of rimiterol. The ipratropium and salbutamol were given double blind in random order and the dose of each was the same during the combination periods. Although there was a significant increase in pulmonary function in all treatment periods over the control, only the 6-minute walking distance was significantly improved in the combination period over treatment with salbutamol and ipratropium individually. This was not due to a progressive rise with time irrespective of the therapy. The results are compatible with a small number of patients benefiting from combination therapy.