Omega-3 fatty acids are being increasingly promoted as important dietary components for health and disease prevention.1,2 These fatty acids are naturally enriched in fatty fish like salmon and tuna and in fish-oil supplements. An increasing number of foods that are not traditional sources of omega-3 fatty acids, such as dairy and bakery products, are now being fortified with small amounts of these fatty acids.2 This recent promotion of omega-3 fatty acids has likely been driven by recommendations for omega-3 fatty acid consumption made by scientific groups such as the American Heart Association.3 The search for the molecular and cellular mechanisms by which omega-3 fatty acids affect health and disease has led to a large body of evidence which suggests that these dietary lipids modulate numerous processes, including brain and visual development, inflammatory reactions, thrombosis and carcinogenesis. An obvious question that someone unfamiliar with omega-3 fatty acids might ask is: How can these nutrients affect so many seemingly unrelated processes in different cell types and tissues? The goal of this review is not to comment on the extent to which dietary omega-3 fatty acids affect health and disease, but rather it is to give an overview of the nature of these dietary components and to present some of the mechanisms by which they may modulate cellular functions.