The thesis deals with Direct-To-Consumers Genetic Testing (DTCGTs) sold on the Internet, and more specifically with the ones for health, physiology, performance and behaviour. This market is booming since the end of the 90’s, and is sparking off controversies which are rooted in multiples scientific and medical uncertainties (“missing heritability”, informed consent, third parties, etc.). It doesn’t require for medical prescription, and health professional consultancy for test data and results is not systematically needed, which is not allowed by some national legislations. For all that, is it a medicalisation phenomenon without physician ?To understand the socio-economic dynamic of this market, we had listed 130 websites (for 60 in the academic literature) and identified 155 entrepreneurs, then we studied the evolution of theirs characteristics. The territorial localisation of the market changed, and european websites are finally as numerous as theirs north-american counterparts. Either in technical devices conception, or in commercialisation, DTCGTs are a sign of the autonomy progression of outsiders from the medical field, if not of their intrusion in this field. Medical dispensing systems are growing alongside of DTC selling, notably through the physician hiring by the DTCGT companies (i.e. hotline selling). Furthermore, some outsiders are relatively new, for they are related to investment funds which are specialized in science and more or less independent from industrial groups. Furthermore, one must notice the presence of informatics and Internet companies which, till now, didn’t really explore the health field. Finally, DTCGT relate also to biomedicalisation and automedicalisation.