Osteoprotegerin (OPG) antagonizes receptor activator of nuclear factor-kappaB ligand (RANKL), the principal regulator of osteoclasts. Of note, OPG-deficient mice display osteoporosis and arterial calcification. Recently, OPG gene polymorphisms have been associated with osteoporosis and early predictors of cardiovascular disease. In this study, we examined OPG gene polymorphisms in 468 men who had absence of coronary artery disease (CAD) or single-, double-, or triple-vessel disease on coronary angiography. Denaturing gradient gel electrophoresis followed by DNA sequencing revealed nucleotide substitutions 149 T-->C, 163 A-->G, 209 G-->A, 245 T-->G, 950 T-->C (all promoter), 1181 G-->C (exon 1), and 6890 A-->C (intron 4), respectively. Although single polymorphisms were not associated with CAD, linkage of polymorphisms 950 and 1181 revealed that haplotypes were overrepresented in men with CAD (chi(2) = 17.05; P = 0.03) with an increased risk of CAD in carriers of genotypes 950 TC/1181 GC and 950 CC/1181 CC (odds ratio, 1.67; 95% confidence interval, 1.02-2.72; P = 0.04). Furthermore, serum OPG levels were correlated with the presence of a C allele at position 950 (P = 0.02). In summary, linkage of genetic variations of the OPG gene at positions 950 and 1181 may confer an increased risk of CAD in Caucasian men.