Crossed immunoelectrophoresis (X-IEP) revealed several abnormalities in serum proteins from patients with adult respiratory distress syndrome (ARDS), tuberculosis (TB), and cystic fibrosis (CF). The two quite different kinds of pulmonary disease, one acute (ARDS) and the other chronic (TB and CF) exhibited serum changes specific for each disease and abnormalities associated with inflammation and pathogenesis, in general. In ARDS sera, most proteins were extremely low, presumably due to leakage into the lungs through damaged tissue, while the acute-phase proteins, orosomucoid, alpha 1-antitrypsin, alpha 1-antichymotrypsin, and haptoglobin, were markedly high when compared to the overall protein pattern. The extremely high alpha 1-antichymotrypsin values were not seen in corresponding TB and CF sera. Numerous TB patients had elevated alpha 1-antitrypsin, alpha 1-antichymotrypsin, and haptoglobin, but only the alpha 1-antitrypsin population mean was significantly different from normal. Gc-globulin, ceruloplasmin, and beta-lipoprotein were higher and alpha 1-lipoprotein and inter-alpha-trypsin inhibitor lower than normal. All other quantitative serum changes were not statistically significant. Surprisingly, all TB patients belonged to the Gc-1-1 genotype in contrast to the Gc-1-1, Gc-1-2, Gc-2-2 polymorphisms of the other populations. CF homozygote sera revealed statistically significant increases in the acute-phase proteins, alpha 1-antitrypsin, alpha 1-antichymotrypsin, and haptoglobin, while orosomucoid, transferrin, IgA, and IgG tended to be higher than normal. The tendency for higher levels of transferrin indicated possible iron deficiency in some patients. In contrast, prealbumin, alpha 1-lipoprotein, and inter-alpha-trypsin inhibitor were significantly depressed in CF patients. CF heterozygotes shared the decrease of alpha 1-lipoprotein with the patients while exhibiting small but significant depressions of alpha 2-macroglobulin and IgG. Though not statistically significant, lowered concentrations of alpha 1-antitrypsin were evident for the heterozygotes.