BACKGROUND Inhalation injury increases morbidity and mortality in burn patients. Patients with inhalation injury present with large differences between end-tidal CO2 pressure and [Formula: see text], an indirect measure of dead space. We aimed to investigate the relationships between increased dead space and inhalation injury outcomes. METHODS This retrospective study included 51 adult subjects with burns and inhalation injuries. Demographics, size of burns, length of stay, ventilator days, blood gas results, end-tidal CO2 pressure, presence of ventilator-associated pneumonia, and mortality data were collected. Modified Baux scores and ratios of alveolar dead space to alveolar tidal volume ([Formula: see text]/[Formula: see text]) were calculated. Independent t tests were used to compare mean [Formula: see text]/[Formula: see text] of survivors to that of subjects who died and between subjects with and without pneumonia. The relationships between [Formula: see text]/[Formula: see text] and ventilator days or modified Baux score were assessed with bivariate correlation analysis. RESULTS Our population had a mean age of 52 y and an average burn size of 17.5%. The average length of stay and ventilator days were 12 d and 3.8 d, respectively. The mean modified Baux score was 87. The mean [Formula: see text]/[Formula: see text] was 0.38. Ten subjects died, and 6 subjects had pneumonia. The [Formula: see text]/[Formula: see text] of survivors was significantly smaller for survivors than for subjects who died (0.34 vs 0.52, P = .03). No significant difference was observed between subjects with and without pneumonia (0.36 vs 0.47, P = .26). [Formula: see text]/[Formula: see text] correlated significantly with modified Baux score (r = .524, P < .001). CONCLUSIONS Alveolar dead space ([Formula: see text]/[Formula: see text]) is easily calculated from [Formula: see text] and end-tidal CO2 pressure and may be useful in assessing severity of inhalation injury, the patient's prognosis, and the patient's response to treatment.