Ten patients with chronic bronchitis (Medical Research Council definition) completed a double-blind placebo-controlled study comparing 400 micrograms, 1 mg, 1.6 mg and 2 mg salbutamol powder. Response was measured by spirometry, peak expiratory flow rate, heart rate and tremor at intervals up to 4 hours post-inhalation. Pulmonary function results showed a trend towards higher doses producing improved response and a longer duration of action, with bronchodilatation following 2 mg significantly greater than 400 micrograms. Seven patients developed or had an increase in tremor following a single dose of 2 mg and in one this was considered to be severe. No adverse effects were recorded on ECG.