In the light of supposed increasing demand for science by companies, the relative difficulties in many countries of recent science PhD graduates in finding employment in companies seem to represent a paradox. We can wonde what are the factors that tend to limit the entry of PhD graduates into companies. This article looks at the recruitment and the careers of researchers in industry (emphasizing the first aspect) using original surveys carried out in companies, in France, Spain and the UK. The comparison of the case studies carried out in the three countries mentioned above should enable a better understanding of the functions filled by R&D activities within companies. Our main hypothesis is that these functions could explain the recruitment policies and the particular situation of PhD graduates. These three questions run through this article : to what extent do company research centres need to employ science PhD graduates ? What is the central logic, mainly in France, behind the differences in the recruitment at PhD level and the recruitment of graduates from shorter diplomas (and in particular those from the élite engineering schools) ? In what way does the organization of research and development whithin companies have an effect on the recruitment of researchers ? Our case studies allow us to make the distinction between at least two types of laboratories (with each having their own type of recruitment) : the central breeding ground laboratory where the recruitment of PhD graduates is limited (due to the fact that they can be used less in non-research position than engineering graduates) ; laboratories that work in close liaison with university research and have a large proportion of PhD graduates. These results are discussed in the context of change in the management of functions of generating, assimilating and transferring technological knowledge.