Background Smoking marijuana has been reported to increase risk of myocardial infarction (MI) immediately after use, but less is known about the long-term impact of marijuana use among patients with established coronary disease. Methods The Determinants of MI Onset Study is a multicenter inception cohort study of myocardial infarction (MI) patients enrolled in 1989 to 1996 and followed up for mortality using the National Death Index. In an initial analysis of 1,935 MI survivors followed up for a median of 3.8 years, we found an increased mortality rate among marijuana users. The current article includes 3,886 Determinants of MI Onset Study patients followed up for up to 18 years. We used Cox proportional hazards models to calculate the hazard ratio and 95% CI for the association between marijuana use and mortality and a propensity score matched analysis to further control confounding. Results Over up to 18 years of follow-up, 519 patients died, including 22 of the 109 reporting marijuana use in the year before their MI. There was no statistically significant association between marijuana use and mortality. Compared with nonusers, the mortality rate was 29% higher (95% CI 0.81-2.05, P =.28) among those reporting any marijuana use. Conclusions Habitual marijuana use among patients presenting with acute MI was associated with an apparent increased mortality rate over the following 18 years that did not reach nominal statistical significance. Larger studies with repeated measures of marijuana use are needed to definitively establish whether there are adverse cardiovascular consequences of smoking marijuana among patients with established coronary heart disease.