There are different types of clinical trials:

• A treatment trial tests new treatments, such as a medication or a surgical technique.

• Prevention trials look for better ways to keep people from getting a specific disease.

• Diagnostic trials are used to find better tests or procedures to make a diagnosis.

• Screening trials test the best detection methods.

Quality-of-life trials are focused on comfort and life issues of those with a chronic condition.

Source: The National Institutes of Health.