We investigated the relationship between plasma levels of fibronectin and other acute-phase reactant proteins such as C-reactive protein, alpha-1 antitrypsin, ceruloplasmin, and transferrin in children with severe septicemia. The study included 33 septicemic patients and 10 normal children. Mean plasma fibronectin level was significantly lower in patients on admission (204.7 +/- 57.3 mg/dl), and was higher after recovery (349.3+/-89 mg/dl), than in normal children (300.2+/-65 mg/dl). No significant difference was found between the mean plasma fibronectin levels of patients with and without meningitis. After the recovery, fibronectin correlated positively with age: No correlation was found between plasma fibronectin and C-reactive protein, transferrin, ceruloplasmin, or alpha-1 antitrypsin levels at any stage of the disease. We concluded that fibronectin has no modulating effect on acute-phase responses of these proteins in severe septicemia.