Background: All humans have the right to receive a thorough medical attention, and should not be discriminated. Aims: To determine if there is a significant relationship between Medical Oaths that commit to the principle of no discrimination in health care and the time, origin and source of the modifications to the Hippocratic Oath. To specify which are the conditions for no discrimination. Materials and Methods: Fifty Oaths found in different articles and publications were analyzed and selected considering their historical context. Results: Of the fifty Oaths that were analyzed, nineteen express a commitment towards no discrimination, whereas one of the texts is discriminatory. The only significant relationship found was the origin and source of the texts. The most frequently discriminating factors found are social class, religion, nationality and race. At present, other factors can be found such as ideology, moral, aptitude, sex and political and sexual preferences. Conclusions: The commitment towards no discrimination is not widely found in Medical Oaths of all times (30/50). According to the bioethics principle of justice, physicians should find the limit of their obligation as doctors in providing medical assistance to everyone alike, wealthy or poor; Christians, Hebrews or Muslims; men or women; children, adults or old; with or without infectious diseases. Non discrimination should be a vow that physicians must be willing to take despite any of the factors that could influence health care (Rev Méd Chile 2003; 131: 799-807)