Since 1992, French clinical research centers (CRC) allow physicians and researchers to develop clinical and therapeutic research on humans in public hospitals. Created by the National institute for health and medical research (Inserm) in collaboration with public hospitals, their history give us the opportunity to describe the complex interactions in France between fundamental and clinical research. Why does therapeutic research need CRC? What can be done in these structures that cannot be done in hospital wards? Medical research is an hybrid practice torn between fundamental and clinical methodologies and objectives. To solve this tension, CRC are << trading zones >> (Galison, 1997): intermediate areas where physicians and researchers can develop -common languages and methodologies to coordinate their practices and objectives. CRC also become essential to support the ethical, legal and administrative constraints of therapeutic research. double dagger.