Objective: The aim of this study was to determine if the metabolic syndrome (MetS) or other risk factors might be common among young women with nonfatal myocardial infarction (MI). Methods: A matched case-control study using a structured interview and questionnaires, plus analysis of conventional and nonconventional risk factors for MI in serum or plasma was carried out at a teaching hospital. Subjects were 40 women with nonfatal MI at or before age 45 and an equal number of age-matched, ethnicity-matched, and smoking-matched female control subjects. Results: Cases and control subjects were not significantly different with regard to serum or plasma levels of homocysteine, anticardiolipin antibodies, β2-glycoprotein I, prothrombin, folate, vitamin B12, high-sensitivity C-reactive protein (CPR), fibrinogen, amyloid A, plasminogen activator inhibitor type 1 (PAI-1), or tissue plasminogen activator (tPA) antigen levels. Compared with matched controls, cases had a higher rate of obesity (37% vs. 12%, p = 0.02), a higher proportion of fasting glucose ≥110 mg/dl (9% vs. 1%, p = 0.01), and higher overall insulin resistance (27% vs. 5%, p = 0.007. Type 2 diabetes tended to be more common in cases (17% vs. 5%, p = 0.10. Cases were also more likely to be hypertensive (35% vs. 12%, p = 0.04) and dyslipidemic (80% vs. 42%, p = <0.001) and to have higher triglyceride levels (110 ± 13 mg/dl vs. 96 ± 12, p = 0.02. Overall, after controlling for weight, cases were 4.7 times more likely to have three or more diagnostic criteria of the MetS than matched controls: chisquare = 7.2, OR = 4.7, 95% CI (1.3, 25.3), p = 0.008. Conclusions: Although this study may have been underpowered to recognize the contribution of other risk factors, we found that the dominant predictor of nonfatal MI in young women was the MetS. Screening young women with central obesity for other parameters of the MetS may help reduce the risk of MI at an early age.