This paper deals with the changes in medical research due to new methodologies and technologies. The author shows that these changes generate many problems regarding data protection (DP) and right of privacy. The legal problems are mainly related to the criminal protection regarding medical secret. The DP laws extend this protection to all steps of information treatment. Since in Switzerland, the DP legislation is still to be completely developed, the author bases himself on the constitutional law to know how far the research activities have to take account of DP requirements and, inversely, how far the DP laws have to provide for less binding measures in the field of research. It is by far preferable to conduct researches with completely anonymous data. When not possible, according to the constitutional principle of interests' balance, measures have to be taken in order to make possible the formal consent of the patient, or to replace this consent by external control of the research project and by security measures.