Good cholesterol is the informal name for cholesterol carried in the blood by high-density lipoprotein (HDL) — the fraction considered protective against heart disease. HDL particles scavenge excess cholesterol from tissues and artery walls and ferry it back to the liver for excretion, a process called reverse cholesterol transport. Higher HDL levels are associated with lower cardiovascular risk, while low HDL marks higher risk — though drugs that raise HDL have disappointingly failed to cut heart attacks, suggesting the relationship is more complex than the nickname implies. Exercise, moderate alcohol, and replacing saturated fats with unsaturated ones tend to raise HDL; smoking and trans fats lower it. Doctors read it alongside LDL and triglycerides, never alone.