Post-harvesarvest operations are part of a system that includes all the steps, factors and actors from production to consumpttion. Therefore, a systems approach must be adopted when analysing constraints and introducing improvements. A methodology to analyse the constraints of post-harvest systems has been developed by the Food and Agriculture Organisation of the United Nations (FAO) and the Deutsche Gesellschaft fur Technische Zusammenarbeit (GTZ) GmbH, with the support of the Centre de Cooperation Internationale en Recherche Agronomique pour le Developpement (CIRAD) and the Group for Assistance on Systems relating to Grain After-harvest (GASGA). Applying the systems approach in the field of roots and tubers (R&T) has shown that there is considerable potential for promoting R&T processing and marketing in order to generate income. GTZ's root and tuber development guides arewill be practice-oriented extension leaflets that show how rural families can make best use of R&T. Each issue of this series is is based on practical experience gained in the post-harvest research and development work conducted by many partners, especially in West Africa. Partners include the International Institute of Tropical Agriculture (IITA), national research institutes and universities and GTZ projects in countries such as Benin, Cameroon, Ghana, Kenya, Nigeria, Tanzania and Togo. R&T commodities are of outstanding importance as staple foods and cash crops for the rural population in Africa. In some countries in tropical Africa, the nutrition of the entire population depends to a large extent on dishes prepared from R&T crops. Processing and marketing of R&T is one of the rare income-generating activities accessible to rural women, especially in Africa.