Rice yellow stem borer (Scirpophaga incertulas Wlk)(rice YSB) is one of the most important insect pests in rice (Oryza sativa L.). Plant damage caused by the pest attack in all growth stages could significantly reduce yield. Cry toxins from Bacillus thuringiensis are known to be effective against rice YSB, therefore transgenic rice events cv Rojolele harbouring the cry1B:: cry1Aa fusion genes driven by the maize ubiquitin promoter have been developed to improve rice resistance. To determine that the resistant traits has been stably inherited and expressed, in-planta and in-vitro bioassays of the T10 generation were performed on 6 independent transgenic rice events using the 1 st instar larvae of rice YSB. In-planta bioassay was performed on 5-week-old rice plants grown in pots in a transgenic glasshouse, in 7 replicates. Each plant was invested with 20 1 st instar larvae of rice YSB. The in-vitro bioassay was performed using the stems of the transgenic rice events against 10 1 st instar larvae of rice YSB, in aerated Petri dishes in a culture room under room temperature, in three replicates. Results showed that the T10 generation of the transgenic rice events stably maintained the transgene integration and their resistance against the rice YSB.