Serum or plasma histidine-rich glycoprotein (HRGP) levels were determined in several conditions. In normal volunteers, HRGP levels did not correlate with either plasminogen contents or plasminogen activity, although HRGP has been believed to be a modulator for fibrinolysis system. In acute inflammation, HRGP levels in serum changed as a negative acute phase reactant, which was also confirmed after surgical operation. At the time of demonstrating decreased HRGP values, expression of HRGP fragment was studied using heparin-Sepharose beads. However, no new fragments were detected, suggesting that the decrease was not due to enzymatic destruction. On the other hand, in patients with rheumatoid arthritis (chronic inflammation), HRGP levels were similar to those in control subjects. As HRGP is a potent heparin antagonist, HRGP levels in plasma during hemodialysis with heparin were studied. Both levels of HRGP and albumin increased after hemodialysis in a similar degree due to concentration, indicating that turnover of HRGP was not altered in short period after heparin administration.