A prevalence study was undertaken to determine whether aerosol equipment used at home by patients with cystic fibrosis (CF) could provide a reservoir for Pseudomonas aeruginosa or Pseudomonas cepacia. Home maintenance of this equipment was also evaluated for its relationship to contamination. In nine of 36 patients, Pseudomonas species were isolated from one or more pieces of home equipment. Only patients colonized with P. aeruginosa had contaminated equipment. P. aeruginosa was recovered from equipment used by five patients; no P. cepacia was recovered. Aerosolization masks were the most commonly contaminated pieces of equipment (20%), followed by nebulizers (17%), medication syringes (10%), connective tubing (6%), and saline solution (4%). Nebulizers and syringes were significantly more likely to be contaminated if they had been in use for 1 month or longer; nebulizers and masks were more likely to be contaminated if they were cleaned or were rinsed only with tap water after use. We conclude that equipment may serve as a reservoir to reintroduce or perpetuate colonization of some patients with CF, but that contamination of equipment with P. aeruginosa is not common.