Although home nebulizers are widely used to deliver bronchodilator medication to patients with asthma and chronic obstructive pulmonary disease (COPD), the long-term benefits and hazards are unknown. The present authors have previously reported a prospective 12-month study of home nebulizer use involving 49 patients (15 asthma, mean forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC) 1.3/2.1 1; 34 COPD, mean FEV1/FVC 0.7/1.8 1). Thirty-two of these patients were treated with long-term domiciliary nebulized bronchodilator treatment, the other 17 patients chose metered dose inhaler (MDI) therapy. The present paper reports the progress of these patients over 5 yr. Five-year survival was similar in both groups (nebulizer users 56%, MDI users 53%). Most deaths were due to respiratory failure (14 deaths) or lung cancer (four deaths). Survival was determined mainly by FEV1 (R = 0.54, P = 0.0001) and age (R = -0.47, P = 0.0007). Laboratory lung function tests (16 nebulizer users) showed that FEV1 and FVC were still higher than pre-nebulizer baseline measurements after 36 months of nebulizer use, but PEFR had fallen by 7%. Twenty-one of 23 surviving nebulizer users completed a questionnaire after 36 months of treatment. All used their nebulizer at least once per day and 20 of 21 patients reported that they still obtained full benefit from each nebulized treatment. The morning peak flow response to nebulized treatment was the same at baseline and at 36 months (48 1 min-1). All patients remained breathless (mean subjective score 4.8 on seven-point scale) but the subjective response to nebulized treatment was unchanged at 36 months. Tachyphylaxis did not develop among 13 patients who underwent repeated reversibility studies using 200 micrograms of salbutamol at 6, 12 and 36 months. It is concluded that home nebulizer therapy is safe and effective for a small number of carefully selected patients with severe asthma or COPD, who have been evaluated by a rigorous home nebulizer assessment protocol prior to commencing home nebulizer therapy.