Medical malpractice occurs when a physician acts negligently toward their patient, and as a result, causes harm or fails to appropriately address a condition. Therefore, an error is not necessarily considered to be malpractice, but a mistake that would not be expected from a reasonable physician would. Less frequently, a doctor may habitually or repeatedly exercise sub-standard skill or care in the course of treating their patients, which under the right circumstances can make a class action proceeding brought on behalf of numerous patients injured under similar circumstances appropriate.

Another form of medical negligence involves the lack of informed consent. A patient is entitled to be advised of their condition, the recommended course of treatment, and any risks of treatment. If a patient undergoes medical treatment that they did not fully understand or consent to, they may have a claim for medical negligence.

Regardless of its form, in Canada, medical malpractice has proven to be high risk litigation, given the legal protections that Canadian law affords the medical profession, and the vigorous defence style of the Canadian Medical Protective Association, which defends claims on behalf of doctors.