Serum levels of soluble Fas, soluble Fas ligand, and nuclear matrix protein (NMP) were measured in 38 patients with ischemic heart disease before and after coronary angiography or coronary intervention. Serum levels of soluble Fas, soluble Fas ligand and NMP were determined by enzyme-linked immunosorbent assay. Patients one week after undergoing stent implantation had much higher levels of soluble Fas ligand and significantly lower levels of soluble Fas than patients without coronary intervention. Serum levels of soluble Fas ligand and NMP in patients with coronary restenosis were significantly higher than those in patients without restenosis. Serum levels of soluble Fas and soluble Fas ligand in patients one week after undergoing stent implantation who had coronary restenosis were markedly lower and higher than in patients without restenosis, respectively. Serum levels of soluble Fas ligand were positively correlated with NMP in those patients. These results indicate that coronary restenosis might be affected by the Fas/Fas ligand system. We conclude that measurement of soluble Fas, soluble Fas ligand and NMP is useful for determination of coronary restenosis in patients with ischemic heart disease.