The standard of care is the basis upon which negligence and fault are determined in medical malpractice lawsuits. It refers to the level of care, skill, and knowledge that is expected and should be found in all physicians of a particular field, in a particular region, acting in similar circumstances. Substandard care, treatment, and surgery occur when a doctor fails to meet this standard. It should be noted that the qualification of "region" is no longer as important as it once was due to national board exams and certifications. These have given rise to a more consistent standard of medical professionalism across the country.

There is a basic level of skill and knowledge that is expected of all licensed physicians. That is, they should all be about to diagnose and treat basic injuries and illnesses; one does not need to be a heart specialist to administer CPR to an individual suffering from a heart attack. However, it would not be expected that all doctors would react to a heart attack with the same expertise of a heart specialist. In a similar vein, a specialist with access to the most advanced and cutting edge tools would be held to a higher expectation than one that did not.

There are difficulties specific to suing a doctor for substandard care, treatment, or surgery. Physicians often refuse to testify against fellow physicians, which is a frequent frustration to lawyers. Because of this, it is often a challenge to locate an unbiased, expert witness who will declare the doctor negligent or the care/treatment/surgery substandard. This is because doctors, even if they practice on opposite coasts, may come in contact with each other at conferences, fellowship programs, board certifications, or other types of meeting and collaboration.