We have previously reported that keratinocyte growth factor (KGF) attenuates α-naphthylthiourea-induced lung injury by upregulating alveolar fluid transport. The objective of this study was to determine the effect of KGF pretreatment in Pseudomonas aeruginosa pneumonia. A 5% bovine albumin solution with 1 μCi of 125I-labeled human albumin was instilled into the air spaces 4 or 24 h after intratracheal instillation of P. aeruginosa, and the concentration of unlabeled and labeled proteins in the distal air spaces over 1 h was used as an index of net alveolar fluid clearance. Alveolocapillary barrier permeability was evaluated with an intravascular injection of 1 μCi of 131I-albumin. In early pneumonia, KGF increased lung liquid clearance (LLC) compared with that in nonpretreated animals. In late pneumonia, LLC was significantly reduced in the absence of KGF but increased above the control value with KGF. KGF pretreatment increased the number of polymorphonuclear cells recovered in the bronchoalveolar lavage fluid and decreased bacterial pulmonary translocation. In conclusion, KGF restores normal alveolar epithelial fluid transport during the acute phase of P. aeruginosa pneumonia and LLC in early and late pneumonia. Host response is also improved as shown by the increase in the alveolar cellular response and the decrease in pulmonary translocation of bacteria.