There are several reasons to modify the composition (notably fatty acid composition) of foods of animal origin. These reasons are: 1. the growing incidence of chronic diseases in Europe, 2. the growing evidence of health-promoting effects of bioactive components of animal origin such as polyunsaturated fatty acids (PUFA) and conjugated linoleic acid (CLA) isomers, 3. the development of nutritional strategies to modify animal product composition, and 4. the advent of the idea of functional foods in Europe. This review presents current examples of nutritional enrichment of foods of animal origin (dairy products, meat and eggs) with PUFA or CLA. Moreover it presents examples of health-related (functional) effects of the modified foods in experimental animals and humans. Feeding these foods to animal models or humans confirmed their functional properties, e.g., anti-obesity, anti-atherogenic and anti-carcinogenic effects. It was repeated after the European Consensus Document (Diplock et al., 1999), that the most pertinent aspect in communicating of health-related benefits of functional foods is that any claim of their functionality must be scientifcally-based, i.e. it must be both objective and appropriate. Therefore the development of functional foods must rely on identification and validation of relevant biological markers of particular target functions and (or) the risk of a particular disease.