Members of the genus Pseudomonas have a multitude of industrial and agricultural applications and have been implicated in human disease. Because inhalation exposure of humans to these strains during production or application is possible, it is important to determine if there are any adverse health effects associated with these environmental isolates. In the study, strain CD-1 mice were administered P. aeruginosa strain AC869 or P. cepacia strain AC1100 intranasally (i.n.). Morbidity, mortality, and the fate of the microorganisms in the lungs, nasal cavity, and G.I. tract were investigated for 14 days. The LD50 was determined to be 2.7 x 10 to the 7th power CFU. When mice were dosed i.n. with 1.6 x 1000, no overt adverse health effects were observed and the dosed strain was cleared from the lungs and G.I. tract within one day but was detectable in the nasal cavity for 14 days. When mice were treated with 1.6 x 10 to the 7th power CFU, slight morbidity was observed and strain AC869 persisted in the intestinal tract and nasal cavity for 14 days but was absent from the lungs after day 7. P. cepacia strain AC1100 was cleared from the G.I. tract and nasal cavity 2 days after i.n. challenge with 5.3 x 10 to the 8th power CFU, but remained in the lung for 7 days post-treatment. The intestinal tract and nasal cavity, therefore, can serve as reservoirs for environmental pseudomonads upon pulmonary exposure.