OBJECTIVE: The purpose of this study was to analyze the interrelationship among oxidation, myocardial infarction (MI), and type 2 diabetes in a population-based case-control study of MI. RESEARCH DESIGN AND METHODS: Participants were 1,709 individuals from western New York: 257 women and men with incident MI and 1,452 healthy control subjects (aged 35-70 years). Lipid peroxidation was measured by plasma levels of thiobarbituric acid reactive substances (TBARS). History of type 2 diabetes was determined by self-reported history of medical diagnosis. RESULTS: In multivariate analyses, there was no significant difference in TBARS levels between case and control subjects in both sexes. In subgroup analyses by diabetes status, diabetic subjects, regardless of MI status, exhibited significantly higher TBARS values than nondiabetic subjects. For diabetic women, TBARS values were 1.84 and 1.83 nmol/ml for case and control subjects, respectively. Values for nondiabetic women were 1.29 and 1.31 nmol/ml, respectively. In diabetic men, values were 1.65 and 1.97 nmol/ml for case and control subjects, respectively. Values for nondiabetic men were 1.36 and 1.36 nmol/ml, respectively. CONCLUSIONS: Whereas type 2 diabetes may be an important correlate of lipid peroxidation, clinical coronary heart disease may not.