Abstract Lots of 200 eggs of Sitotroga cerealella (Olivier) were placed on 10 g samples of 780 varieties of rice from the U.S.D.A. World Collection. An average of 91% of the eggs hatched and between 1 and 83% of the larvae from these reached the adult stage and emerged. Less than 10% survived in 102 varieties. Graphic data exhibit a bimodal shape, indicating that two resistance bases operated against these insects; both apparently acted to prevent kernel entry by the freshly hatched larvae.