The longterm performance of multi-generations or life span was assessed using genetically modified (GM) insect-resistant Bt11 corn. Diet containing 68% of GM Bt11 or non-Bt isoline with sufficient nutrient composition was fed to male and female ICR mice through 5 generations. The results of growth, mating, gestation, milking periods, reproduction and life span were not different between the GM Bt11 and non-Bt fed groups. The percentage of embryonic death, litter size, newborn sex ratio and body weight (21-60 days after birth) were not different between these groups. The life span of the third-generation mice did not differ over 1,072 days of observation. In addition, there was a tendency for a weight decrease among each group as the generations progressed, but there was no significant difference in performance among each group in each generation of mice.