Varriety use and development, seed production and storage by farmers under local conditions, and seed exchange mechanisms are presented as the three principal components of a dynamic system that forms the most important seed source of food crops for small farmers in developing countries. The information on this topic is based on a literature review and a case study. Analysis of strengths and weaknesses of local seed systems leads to the conclusion that local seed systems and the formal system are complementary. Integrated approaches in breeding, and seed production and distribution show to have promising potential for improving seed supply for small farmers.