Dietary fat is an important source of nutrients and is proven to be beneficial to human health, however excess intake of certain types of fats has also been associated with the development of many chronic diseases. Written by a group of lipid experts who participated in the 2004 AOCS-JOCS Joint Symposium on Bioscience, the material contains information from lectures presented in the meeting, as well as invited papers from authors who could not attend. This text discusses the effects of several different dietary fats on the development of chronic diseases, such as cardiovascular disease, diabetes, cancer, inflammation, and immune functions.