Alpha-linolenic acid (ALA) is an n-3 polyunsaturated fatty acid found mainly in plant sources, including flaxseed oil, canola oil, and walnuts. Although substantial evidence indicates that consumption of long-chain n-3 polyunsaturated fatty acids from seafood reduces the risk of coronary heart disease (CHD), the effect of ALA intake on CHD risk is less well-established. ALA may reduce cardiovascular risk through a variety of biologic mechanisms, including platelet function, inflammation, endothelial cell function, arterial compliance, and arrhythmia. Although clinical benefits have not been seen consistently in all studies, most prospective observational studies suggest that ALA intake reduces the incidence of CHD, and two randomized trials have demonstrated that a dietary pattern that includes fruits, vegetables, whole grains, nuts or legumes, and ALA-rich foods substantially reduces the recurrence of CHD events. Additional observational and clinical studies will help establish the effects of ALA on CHD risk and determine whether such effects vary based on gender, duration of intake, background dietary intake of seafood, or other factors. Presently, the weight of the evidence favors recommendations for modest dietary consumption of ALA (2 to 3 g per day) for the primary and secondary prevention of CHD.