Doing field research in a « colonial siuation » reveals the relations existing between ethnology and geography. In spite of different scientific traditions both disciplines were brought closer to each other through the difficulties they encountered and through their field researchers – in increasing number due to the development of research institutions in French West Africa in the fifties –, but they did not really develop a pluridisciplinary reflexion. The various works produced in both disciplines – from experts’ works to critical reviews of the colonial situation let appear divisions between them. The « colonial field » is peculiar in that it enables researchers to bring to light their experiences, choices and moral or political commitments and thus to dispose of or elaborate new hypotheses to grasp their field and possibly reinterpret it. In spite of these convergences, partly due to a same colonial context, were the ethnologic and geographic disciplines not really involved in a pluridisciplinary project at the end of the fifties.