The study relates village seed systems to biological diversity of millet crops grown by farmers in the semi-arid lands of Andhra Pradesh and Karnataka, India. In these subsistence-oriented, semi-arid production systems the environment is marginal for crop growth and often there is no substitute for millet crops. Across communities, farmers grow 13 different combinations of pearl millet, sorghum, finger millet, little millet, and foxtail millet varieties, but individual farmers grow an average of only 2–3 millet varieties per season. The “village seed system” in this study refers to all channels through which farmers acquire genetic materials, separate from or in interaction with the commercial seed industry, observed at the local level. Data are compiled through household surveys and interviews with traders and dealers in village and district markets. Based on the concept of the seed lot, several seed system parameters are defined and measured by millet crop. Most seed transactions, including gifts of seed, appear to be monetized. Seed supply channels differ by improvement status of the genetic material. Regression results confirm that seed system parameters are statistically significant determinants of the spatial diversity of millet crops measured at the village level. Furthermore, both the trade through weekly village markets (shandies) and through the formal seed supply channel contribute positively to the breadth of genetic materials in these communities. Ways should be found to strengthen and improve the overall efficiency of the seed system, including both formal and informal channels, in order to reduce the costs to farmers of procuring and managing diverse crop varieties." -- Authors' Abstract"