Seeds of Rangpur lime and sweet orange, the two species most used as rootstocks in the State of São Paulo, Brazil, were stored under different conditions in order to find out the best for the conservation of their viability. It was found that seeds of both species remained viable longest when stored at 2-3°C in closed (not sealed) containers with very humid air. Under these conditions, Rangpur lime and sweet orange seeds could be kept successfully for 14 and 11 months, respectively. The importance of moisture content and temperature effects on the viability of these seeds is shown. It is likely, however, that other factors may be involved, such as growth of fungi and bacteria, rate and temperature of drying, and gaseous exchange as has been suggested by other workers.