The goals with this paper are to review the processes that regulate seed banks in agroecosystems, their horizontal and vertical distribution in the soil, as well as to present a simple methodology for the study of the seed banks size, regeneration potential and seed spreading. We focus mainly on internal and external factors regulating growth and exhaustion of seed banks, the impact of tillage on transitory and permanent banks and aspects related to germination and dormancy of seeds. In agroecosystems, the propagule banks constitute the primary resource ensuring the perpetuation of weeds; even if only a small portion remains, there will be weeds during the next growing season. A broad knowledge of these banks and their dynamics might prove useful for future rational schemes of weed management.