Many lives could be saved if GPs followed guidelines for reducing cholesterol in patients at high risk of heart disease, research suggests.
A study of 25,250 patients in Germany found that only about half were assigned the correct targets for lowering cholesterol.
Doctors believe the findings, published in the European Heart Journal, may apply in the rest of Europe.
Women are most at risk of being given insufficient treatment, they say.
The study found that about 50 to 80 fewer heart attacks, strokes and heart disease-related deaths per 1,000 patients could be avoided over a 10-year period if all doctors adhered to the guidelines on cholesterol-lowering targets.
Patients were more likely to be given correct targets if they had a history of heart attacks, coronary heart disease and diabetes, the researchers found.
Professor Heribert Schunkert, a clinical cardiologist who led the research in Lubeck, Germany, said the core question involved the perception of patient risk.
"Women are often perceived as having a lower cardiovascular risk compared to their real risk, and this may lead to insufficient treatment," he said.
"This aspect has also been reported in other regions in the world."
Professor Ian Graham, head of cardiovascular medicine at Trinity College Dublin. and a spokesman for the European Society of Cardiology said the UK did better when it came to giving out correct cholesterol targets.
But he cautioned: "There is a general principle of guideline fatigue. GPs are bombarded by targets.
"It's important to make guideline information as easy and accessible as possible."
Cholesterol is a fatty substance known as a lipid. It is carried in the blood on proteins called low-density lipoproteins (LDL).
LDL is known as bad cholesterol because it deposits cholesterol in the lining of the arteries.
The more LDL a person has, the more likely they are to develop heart disease.
Lowering cholesterol using drugs, diet and other lifestyle measures is an important preventative measure.
The government recommends that total cholesterol levels should be less than 5mmol/l.
On average, men in England have a cholesterol level of 5.5mmol/l and women have a level of 5.6mmol/l.