Investigation of a possible quantitative relationship between the extent of tissue injury due to inhalation of tobacco smoke and changes in concentrations of a number of acute phase proteins were studied in smokers. Smokers showed an acute phase response as indicated by significantly raised serum C-reactive protein levels. Significant lowering of serum albumin levels was also observed in smokers. Serum levels of alpha 1-antitrypsin, alpha 1-antichymotrypsin, alpha 1-acid glycoprotein, transferrin and haptoglobin did not show any significant changes due to inhalation of tobacco smoke. Although the C-reactive protein test is non-specific, evidence for elevated levels of C-reactive protein indicates the presence of tissue inflammation.