The present study which started in 1999 is framed in the INCOYAM project. Marketing systems of yam are analyzed in three West- African countries: Cote d'Ivoire, Benin and Nigeria. Surveys have been carried out on urban (wholesales and retailers) and rural (collectors) traders. Cities and production regions have been selected in function of their socio-economic characteristics. As a result, in the three countries data has been collected in an important consumption pole, a commercial redistribution pole and a production pole. The degree of precision of the data varies from one country to another due to asymmetric financing. This situation did not allow establishing an equilibrated comparison of yam marketing systems. The three countries commercialize a similar product but their marketing systems and the structures of their marketing chain varies from one country to another.