CASE DESCRIPTION Three 21-week-old sexually intact female sibling domestic shorthair cats were brought to an emergency clinic because of signs of sudden respiratory distress that were noted by the owner after the cats had been confined for approximately 10 hours in a room with an operating ozone-generating air purifier. No other potential toxicant exposures were reported. CLINICAL FINDINGS On initial examination, the 3 cats were severely dyspneic and tachypneic. Pulmonary crackles were audible on thoracic auscultation. Thoracic radiography revealed a marked peribronchial, unstructured interstitial pulmonary pattern that coalesced to a patchy alveolar pattern, consistent with noncardiogenic pulmonary edema. TREATMENT AND OUTCOME A diuretic (furosemide, 2 mg/kg [0.9 mg/lb], IV) and bronchodilator (terbutaline sulfate, 0.01 mg/kg [0.005 mg/lb], IM) were administered, and supplemental oxygen was provided by placing the cats in an oxygen cage at 80% oxygen saturation. By 24 hours after placement in the oxygen cage, all cats had unremarkable respiratory rates and thoracic auscultation findings. Complete resolution of the respiratory signs and radiographic pulmonary lesions was achieved within 48 to 72 hours after initial evaluation. At a recheck examination performed 3 months after initial evaluation, the cats remained free of respiratory signs, and no radiographic pulmonary lesions were detected. CLINICAL RELEVANCE To the authors' knowledge, this was the first reported case of pulmonary toxicosis believed to have been caused by ozone exposure in cats. Associated respiratory signs were successfully and rapidly reversed following oxygen supplementation and medical treatment.