The effect of inhalation of 5 mg of salbutamol by a jet nebulizer and 0.3 mg from a metered aerosol was compared in 20 patients with chronic asthma. Half the patients, randomly selected, received one treatment method on day one and the other on day two. A battery of lung function tests suitable for detecting large and small airways obstruction showed only insignificantly more pronounced bronchodilatation after the use of the jet nebulizer. Neither was a better dilation of small airways with this method obvious. It is concluded that the higher dose by jet-nebulizer is only clinically motivated when the patients cannot perform the deep inhalations and breathholding necessary for efficient use of the dose aerosol.