BACKGROUND: The summarized importance of haemostatic and metabolic variables (insulin, lipids including lipoprotein (a) [Lp(a)] and leptin) in predicting first myocardial infarction, as well as possible interactions among these variables, have not been reported. DESIGN: A prospective case-control study nested within the Northern Sweden Health and Disease Cohort. METHODS: Sixty-two men diagnosed with a first myocardial infarction were sex- and age-matched with 124 controls. Conditional logistic regression was conducted including established risk factors, plasma levels of plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (tPA) mass concentration, von Willebrand factor, insulin, proinsulin, specific insulin, apolipoprotein A-I (apo A-I), Lp(a), and leptin. Interaction analysis was also performed for tPA, apo A-I, Lp(a), leptin and proinsulin. RESULTS: Smoking, low plasma levels of apo A-I and high plasma levels of cholesterol, Lp(a), tPA, PAI-1, proinsulin and leptin were associated with myocardial infarction in univariate conditional logistic regression analysis. High tPA [odds ratio (OR), 21.3; 95% confidence interval (CI), 2.04-222] and Lp(a) (OR, 7.21; 95% CI, 1.31-39.8) and low apo A-I (OR, 0.15; 95% CI, 0.02-0.93) remained significant risk determinants in multivariate analysis with smoking habits, body mass index, hypertension, cholesterol, and diabetes included as covariates. There were non-significant synergic interactions between high Lp(a) and leptin and tPA, respectively, and between high Lp(a) and low apo A-I. CONCLUSION: Plasma levels of tPA, Lp(a), and apo A-I are independently associated with subsequent development of a first myocardial infarction in men.