We studied the influence of the agonal period on the concentrations of acute phase proteins in biological fluids obtained from 26 autopsy cases. We found significant differences for C-reactive protein concentrations in serum and in pericardial fluid, between short and long agonies. The other acute phase proteins studied (alpha-1 antitrypsin, alpha-2 macroglobulin, haptoglobin) failed to show any significant difference in serum and pericardial fluid levels between the two types of agony. The increase in C-reactive protein level in the pericardial fluid is attributed to an "agonal pericarditis" which may result from an agonal myocardial necrosis. Our results could be of interest in forensic medicine.