Coronary heart disease is the principal cause of death in all Western countries. Abnormalities in the serum lipids are one of the major risk factors widely recognised as leading to this epidemic of heart disease. These abnormalities occur very commonly in the general community and in general practice, and practitioners are pre­ vailed upon daily to provide specific advice about diet and cholesterol and to interpret chemical estimations. This is a very emotive area of medicine, one where often the patients most active in seeking advice have the least to gain. On the other hand, there may be young people carrying a severe coronary risk, knowingly or not, who prefer to avoid risk factor in­ tervention. There are strong vested interests in the commercial world who would prefer to overlook any therapeutic value of dietary modification for selected in­ dividuals, and others who see great merit in a particular diet. The pharmaceutical industry has a vested interest in the cholesterol story as well. The individual doctor needs to decide for himself whether the cholesterol issue requires action or not, and for this he needs access to up to date and relevant data. This is one of the purposes of this book. The use of lipid-lowering therapy is usually quite a straightforward exercise for any medical practitioner, once the decision has been taken to initiate it.