Inhalation injury (INHI) associated with thermal injury has been shown to increase the rate of mortality. Several investigators have shown that patients with inhalation and burn injuries will require increased fluid volumes during acute resuscitation when compared with patients with burn injury alone. Other groups have examined the use of lung compliance and airway resistance as predictors of outcome in patients with INHI. We hypothesized that increased fluid requirements would more closely correlate with perturbations in pulmonary performance than with mere presence or absence of INHI or the degree of injury by bronchoscopic criteria. We performed a retrospective chart review during a period of 3 years. We identified 80 patients with suspected INHI that required intubation, mechanical ventilation, and fiber optic bronchoscopy in the first 24 hours of their admission. Variables collected included age, sex, weight and %TBSA burned, as well as blood alcohol level, the presence of head and neck burns and escharotomies, and admission carbon monoxide levels. Patients were classified into five groups according to a grading system of INHI (0, 1, 2, 3, and 4), derived from findings at initial bronchoscopy and based on AIS criteria. The following pulmonary parameters were noted at regular intervals: mode of ventilation, tidal volume, peak inspiratory pressures, mean airway pressures, and compliance. The P:F ratio also was recorded at regular intervals. Total fluid volume infused was noted at 0-, 24-, and 48-hour intervals, and was calculated as ml/kg/%TBSA. Outcomes were measured by in-hospital survival, ventilator days, intensive care unit days, and total length of stay. Patients were well matched for %TBSA among the different bronchoscopic grades of INHI, and those with grades 2, 3, and 4 injuries had a significantly worse survival than those with grades 0 or 1 (P = .03). However, grades 2, 3, and 4 did not have increased acute fluid requirements when compared with grades 1 and 2 injuries. Initial pulmonary compliance likewise did not correlate with acute fluid requirements. However, those patients with a P:F ratio less than 350 at presentation had a statistically significant increase in ml/kg/%TBSA compared with those with P:F >350 (P = .03). They did not have more ventilator days or a statistically worse survival. Fiber optic bronchoscopy is useful in the diagnosis of INHI, and overall survival is worse in those patients with worse grades of injury by bronchoscopic criteria. However, the P:F ratio may be a more accurate predictor of increased fluid requirements during the acute resuscitation.