This contribution will present the emergence of the vocational guidance in Switzerland during the first part of the 20th century. At the beginning of this century, vocational guidance grows in relation with educational sciences' field, particularly in connection with experimental psychology and pedagogy and scientific organisation of work and training. The Swiss case seems especially interesting because it offers contrasting configurations, each Swiss canton having a large autonomy in educational policy. Vocational guidance appears in the beginning of the 20th century linked with social, educational and economical stakes. Changes in work organisation, new needs of output and training meet scientific interests in a expanding disciplinary field of experimental approaches of human behavior. In Switzerland as well as in Europa and in the USA, several private institutes are founded in order to develop vocational guidance as well as scientific organisation of work and training. In 1920, the Geneva Institut Jean-Jacques Rousseau or institute of educational sciences organises the first international congress on this subject. From this moment on, the congresses will regularly take place in several European places. After this first period, in the 1920's, the institutes and the actors start being in competition. The methods are criticized or even called into question. As the scientific credibility is threatened, an ambition appears to organize this new field from a scientific and methodological point of view. Then, until the 1950's, institutional forms linked to vocational guidance appear as well as new connections are created between vocational guidance and educational sciences. The methods evolve, courses and degrees are created in universities as well as professors are appointed. State, especially Board of Education, get more and more involved in the field, creating different structures for training. A new allocation of duties takes place between the different instances in presence and influence the relationship between different disciplines involved in vocational guidance.To better understand the evolution of this relationship, the contribution will answer the following questions. Who are the founders of vocational guidance's institutes ? Where do they come from ? Which is their training and/or academic degree ? Which are the scientific activities of these institutes and which are their applications' issues ? Which relationship settles between vocational guidance, scientific organisation of work and educational sciences and how does it evolve ? Which institutes will get the responsibility of doing research, training and/or professional applications ? The question of the training is also crucial : which knowledge have to be taught ? What are the instances (scientific or professionnal) that are legitimated to define it ? What are at least the different trainings needed to answer the professional issues ?In answering these questions, this contribution will contribute to describe the process that induces the creation of a new scientific disciplines and professional fields of applications in the sphere of educational sciences. The analysis will be based on the examination of several Swiss archives sites belonging to private and State institutions.