Rats were chronically infected withPseudomonas aeruginosaby entrapping viable bacteria in agar beads and intratracheally inoculating the beads into the left lung. The infection was allowed to stabilize over a 10‐d period and the animals were then placed in environmental chambers and exposed to either filtered air or 0.64 ppm ozone (23 h/d) for 14 or 28 d. Rats exposed to ozone had reduced body weight and increased lung sizes and lung weights when compared with animals breathing filtered air. Rats inoculated with beads containing liveP. aeruginosahad increased lung weights when compared with rats inoculated with beads containing heat‐killedP. aeruginosaor controls. Quantitation of total viable bacteria in rats exposed to ozone or to filtered air revealed no significant differences in bacterial numbers. Thus, in this model, chronic exposure to ozone produces increases in lung volume and weight but does not enhance a smolderingPseudomonasinfection.