Newly-diagnosed cases of MI and controls will be interviewed in person to assess medical and behavioral characteristics related to MI risk. A venous blood sample will be obtained and processed into aliquots of plasma and white cells. DNA extracted from the white cells will be tested using the polymerase chain reaction (PCR), PCR/restriction fragment length polymorphisms (RFLP), and oligonucleotide ligation assays to determine the genotypes of interest. Plasma will be tested for lipid, lipoprotein, and homocysteine concentrations. Analyses will address both the overall association between the genotypes and MI risk, along with posited gene-environment and gene-gene interactions.