Eighteen patients (nine asthmatic patients and nine with poorly reversible airflow obstruction) with stable, severe chronic airflow obstruction, completed a four-week randomized, doubled-blind, placebo-control, crossover trial comparing the acute and chronic effects of terbutaline administered by metered-dose inhaler (MDI) and nebulizer (NEB). Equipotent doses of terbutaline were selected from the comparison of separate cumulative dose-response curves for MDI and NEB. The MDI and NEB given acutely produced similar bronchodilatation and improvement in exercise performance. Spirometric indices, 6 min walking distance, symptom scores and extra beta-agonist use were no different between MDI and NEB treatment fortnights in the outpatient study. We conclude that the degree of bronchodilatation achieved in these patients is a reflection of the dose of bronchodilator administered and not the mode of administration. There is no justification for the preferred outpatient use of nebulized bronchodilators in patients with stable chronic airflow obstruction who can use adequate doses of bronchodilators via a metered-dose inhaler.