Background: Infection is still one of the leading causes of death in burn patients. The diagnosis of respiratory tract infection in critically ill burn patients is still difficult. The diagnostic technique of choice remains uncertain, especially because of the lack of a criterion standard by which other diagnostic methods can be compared. Hypothesis: Bronchoalveolar lavage (BAL) and protected bronchial brush (PBB) cultures are not efficacious for the diagnosis of pneumonia in critically ill burn patients. Design: All pediatric patients with burns who died at Shriners Burns Hospital, Galveston, Tex, in the past 10 years were studied. We compared the clinical diagnosis of pneumonia, BAL quantitative culture results, and PBB culture results with autopsy findings. The diagnosis of pneumonia at autopsy was considered the criterion standard, and it was used to calculate the sensitivity and specificity of BAL and PBB cultures. Results: Forty-three patients were studied. Pneumonia was present in 19 (44%) of the 43 autopsies. Pneumonia was diagnosed clinically in 12 (28%) of the 43 patients, and 6 (50%) of them had negative autopsy findings. The sensitivity and specificity of BAL were 56% and 28%, respectively; PBB, 55% and 61%, respectively. The same microorganisms were found at autopsy in BAL cultures, and in PBB cultures in fewer than 10% of the patients. Conclusions: Bronchoalveolar lavage and protected bronchial brush have a low sensitivity and specificity and cannot be relied on by themselves for the diagnosis of pneumonia in critically ill burn patients. The results of these sampling techniques must be interpreted in the context of the overall clinical picture of each individual patient.