Nanogram quantities of a 25-kDa lipase purified from culture supernatants of Pseudomonas cepacia 90ee, a sputum isolate from a cystic fibrosis (CF) patient, were placed in the lungs of healthy rats. The resulting pathological changes included large amounts of proteinaceous exudate, the accumulation of polymorphonuclear leukocytes and red blood cells, and disorganization of alveolar structure. Pseudomonas cepacia 90ee immobilized in agar beads was also placed in the lungs of rats in a model of chronic infection. This resulted in bronchopneumonia and a milder inflammatory response than that elicited by the purified enzyme.