The matrix metalloproteinases appear to play an important role in the development and progression of atherosclerotic lesions. We studied the C-1562T polymorphism of the gelatinase B promoter in relation to coronary artery disease and restenosis after a percutaneous coronary intervention (PCI) in Koreans. To determine the frequency of the C-1562T allele, we examined 63 patients with coronary artery disease who underwent both PCI and 6-month follow-up coronary angiograms (CAGs), and 67 control patients with a normal CAG with respect to their clinical data and genotype. Frequencies of the C/C homozygotes and the non-C/C heterozygotes and homozygotes (C/T and T/T) were 94% and 6% in the normal CAG group, and 76.2% and 23.8% in the patient group, respectively. This gave a relative risk of 0.203 (95% CI: 0.063-0.651, P = 0.005) for coronary artery disease when the C/C genotype was compared with the non-C/C genotype. In the patient groups, the allele frequencies of the C/C and non-C/C were 80% and 20% in the nonrestenotic subgroup, and 71.4% and 28.6% in the restenotic subgroup (P = 0.554). No T/T homozygote was found in any of the groups. We conclude that C/C homozygosity is a potential genetic protective factor for coronary artery disease in Koreans.