The levels of surfactant protein-A (SP-A) and surfactant protein-D (SP-D) in the serum of patients with septic acute respiratory distress syndrome (ARDS) were determined. Patients with sepsis without ARDS were examined as controls. The mean serum SP-A level in the former group was 37.6 +/- 16.2 ng/ml and in the latter group was 31.8 +/- 9.6 ng/ml. The difference between the two groups was not statistically significant. The maximum serum SP-D level was 83.0 +/- 33.9 ng/ml in the control group of patients without ARDS, and 476.3 +/- 391.2 ng/ml in the patients with ARDS. The level in the latter population was significantly higher than that in the former population. No significant correlation was observed between the SP-A and SP-D levels. These results suggest that the serum SP-D levels may serve as a good diagnostic indicator of ARDS in patients with sepsis.