Objective: To describe current patterns of home nebulizer use among patients with cystic fibrosis. Study design: A population-based survey of home nebulizer practices among 227 patients with cystic fibrosis using nebulizers from 1993 to 1994 (Objective 1), and a prospective study of 'typical' home use, including testing of performance and bacterial cultures in nebulizers after use, completed by 36 subjects (Objective 2). Results: Objective 1: 85% of subjects reported using jet and 8% ultrasonic nebulizers (categories not mutually exclusive); 15% used unknown brands. Most jet nebulizers were disposable models, which were used for > 14 days by more than half the subjects. Mixing of medications in a single treatment (other than cromolyn and a bronchodilator) was reported by 28% of patients. Objective 2: no apparent deterioration in aerosol particle size or output rate of returned nebulizers compared with new units was observed. Staphylococcus aureus was cultured from 55% and Pseudomonas aeruginosa from 35% of returned nebulizers. Concordance between nebulizer and sputum cultures was poor. Conclusions: Although not generally tested for reusability, disposable nebulizers are generally used by patients for long periods. Medication mixing is common, although its effects on aerosol properties are unknown. Cystic fibrosis respiratory pathogens are frequently isolated from used nebulizers. Patient guidelines for home nebulizer use need to be established.