We studied lung clearance of aerosolized technetium-labeled diethylenetriamine pentaacetic acid (99mTcDTPA), plasma concentrations of 6-keto-PGF1 alpha and thromboxane B2, and pulmonary edema as indices of lung injury in rabbits exposed to cigarette smoke (CSE). Forty-six rabbits were randomly assigned to 4 groups: control sham smoke exposure (SS, N = 9), sham smoke exposure ibuprofen-pretreated (SS-I, N = 10), CSE (N = 9), sham smoke exposure ibuprofen-pretreated (SS-I, N = 10), CSE (N = 9), and CSE ibuprofen-pretreated (CSE-I, N = 19). Ibuprofen (cyclooxygenase eicosanoid inhibitor) was administered as a single daily intramuscular injection (25 mg/kg) for 7 days before the experiment. Cigarette or sham smoke was delivered by syringe in a series of 5, 10, 20, and 30 tidal volume breaths with a 15-min counting period between each subset of breaths to determine 99mTcDTPA biological half-life (T1/2). In the ibuprofen pretreated group, CSE caused significant decreases in 99mTcDTPA T1/2 and dynamic lung compliance. Furthermore, these changes in lung function were accompanied by severe injury to type I alveolar cell epithelium, pulmonary edema, and frequently death of the rabbits. These findings suggest that inhibition of the cyclooxygenase pathway before CSE exacerbates lung injury in rabbits.