The subject of this thesis is the criminal offense of medical malpractice. The aim of the paper is to legally present and analyze the criminal offense of negligent treatment and to analyze two different systems of responsibility of health professionals and court practice in the Republic of Croatia. In the Criminal Code of the Republic of Croatia, the criminal liability of health care workers is prescribed by special criminal offenses against human health, in accordance with the model of criminal liability of health care workers that is characteristic of all countries of the former Yugoslavia. In order to prove the criminal liability of a healthcare worker, it is necessary to prove the cumulative existence of four elements of a criminal offense (action, being, illegality and guilt) in a particular case. The harmful consequence that occurs must be causally related to the violation of the rules of the health profession and must concern significant damage to health and be the result of a medical error. The criminal offense of medical malpractice must be committed with intent or negligence. In the final paper, they analyzed four cases from judicial practice in which they tried to determine the criminal liability of suspects in cases of the criminal offense of negligent treatment with fatal consequences. It has been shown that the commission of the criminal offense of negligent treatment is difficult to prove, and that the courts rely to a significant extent on the opinions of court experts, ie medical experts, when making decisions.