Fats are present in the body in the form of lipid particles containing cholesterol and triglycerides. Lipid particles can deposit in blood vessels, forming atheromas, blocking blood vessels and leading to heart attacks and strokes. These harmful particles are termed 'atherogenic' particles. Low density lipoprotein (LDL) is the major atherogenic particle. Each atherogenic particle has a protein associated with it called apolipoprotein B (apoB). Cholesterol, triglycerides, and apoB levels can be measured in the laboratory. In this study we focus on patients with raised levels of triglycerides (hypertriglyceridaemia).