Angina refers to the pain arising from lack of adequate blood supply to the heart muscle. Typically, it is a crushing pain behind the breastbone in the center of the chest, brought on by exertion and relieved by rest. It may at times radiate to or arise in the left arm, neck, jaw, left chest, or back. It is frequently accompanied by sweating, palpitations of the heart, and generally lasts a matter of minutes. Similar pain syndromes may be caused by other diseases, including esophagitis, gall bladder disease, ulcers, and others. Diagnosis of angina begins with the recognition of the consistent symptoms. Often an exercise test with radioactive thallium is performed if the diagnosis is in question, and sometimes even a cardiac catheterization is done if the outcome is felt necessary to make management decisions. This is a complex area which requires careful judgment by physician and patient. Angina is a manifestation of coronary artery disease, the same disease leading to heart attacks. Coronary artery disease refers to those syndromes caused by blockage of the flow of blood in those arteries supplying the heart muscle itself, i.e., the coronary arteries. Like any other organ, the heart requires a steady flow of oxygen and nutrients to provide energy for movement, and to maintain the delicate balance of chemicals which allow for the careful electrical rhythm control of the heart beat. Unlike some other organs, the heart can survive only a matter of minutes without these nutrients, and the rest of the body can survive only minutes without the heart-thus the critical nature of these syndromes. Causes of blockage range from congenital tissue strands within or over the arteries to spasms of the muscular coat of the arteries themselves. By far the most common cause, however, is the deposition of plaques of cholesterol, platelets and other substances within the arterial walls. Sometimes the buildup is very gradual, but in other cases the buildup is suddenly increased as a chunk of matter breaks off and suddenly blocks the already narrowed opening. Certain factors seem to favor the buildup of these plaques. A strong family history of heart attacks is a definite risk factor, reflecting some metabolic derangement in either cholesterol handling or some other factor. Being male, for reasons probably related to the protective effects of some female hormones, is also a relative risk. Cigarette smoking and high blood pressure are definite risks, both reversible in most cases. Risk also increases with age. Elevated blood cholesterol levels (both total and low density types) are risks, whereas the high density cholesterol level is a risk only if it is reduced. Possible, but less well-defined factors include certain intense and hostile or time-pressured personality types (so-called type A), inactive lifestyle, and high cholesterol diets. Medications are increasingly effective for symptom control, as well as prevention of complications. The oldest and most common agents are the nitrates, derivatives of nitroglycerine. They include nitroglycerine, isosorbide, and similar agents. Newer forms include long acting oral agents, plus skin patches which release a small amount through the skin into the bloodstream over a full day. They act by reducing the burden of blood returning to the heart from the veins and also by dilating the coronary arteries themselves. Nitrates are highly effective for relief and prevention of angina, and sometimes for limiting the size of a heart attack. Used both for treatment of symptoms as well as prevention of anticipated symptoms, nitrates are considered by many to be the mainstay of medical therapy for angina. The second group of drugs are called "beta blockers" for their ability to block the activity of the beta receptors of the nervous system. These receptors cause actions such as blood pressure elevation, rapid heart rate, and forceful heart contractions. When these actions are reduced, the heart needs less blood, and thus angina may be reduced. The newest group of drugs for angina is called the calcium channel blockers. Calcium channels refer to the areas of the membranes of heart and other cells where calcium flows in and out, reacting with other chemicals to modulate the force and rate of contractions. In the heart, they can reduce the force and rate of contractions and electrical excitability, thereby having a calming effect on the heart. Although their final place in heart disease remains to be seen, they promise to play an increasingly important role. When medications are unsuccessful, or if there is concern about an impending or potential heart attack, coronary bypass surgery is highly successful in reducing symptoms. Whether or not it prolongs survival is questionable for most patients. Angina which is new or somehow different from previous episodes in any way is termed unstable angina. It is considered a medical emergency, and requires urgent attention. Research is active, and careful medical follow-up is important.