Adults of rice stink bugs, Oebalus ypsilongriseus (De Geer, 1773), were collected in activity on the field. They were kept under laboratory conditions to obtain egg masses for biological studies. The leaves of Polygonum punctatum Elliot (Polygonaceae) were the preferred oviposition site. The average number of eggs per batch was 17.1 ± 8.9. The number of eggs per mass ranged from 1 to 37, and the most frequent were those with 12 eggs. A female with non-hibernating morph laid greater eggs-clusters than the females with hibernating morph.