Toxin expression of Cry2Ab was studied in plant parts of Bollgard II cotton genotype MRC 7031 sown under different treatments of nitrogen application and planting dates. The expression was quantified by using Cry2Aa ELISA kit. Mean per cent mortality of one-day-old, 3rd and 5th instar larvae of Spodoptera litura was observed on different plant parts of MRC 7031 and their respective non-Bt cotton genotypes. The study deduced that mean maximum expression (19.24, 20.93 and 20.71 microg g(-1) in leaves, squares and bolls, respectively) of Cry2Ab was observed at higher nitrogen dose @ 300 kg ha(-1) (N3), while it was minimum (18.67, 20.44 and 20.14 microg g(-1) in leaves, squares and bolls, respectively) at low nitrogen dose @ 150 kg ha(-1) (N1). Studies conducted for different planting dates showed mean maximum expression (18.98, 20.72 and 20.42 microg g(-1) in leaves, squares and bolls, respectively) of Cry2Ab during late sown crop (15th May) as compared to early sown crop (15th April), the expression was 18.66, 20.32 and 20.06 microg g(-1) in leaves, squares and bolls, respectively. Quantitative expression of Cry2Ab was found to vary among different plant parts, i.e more in squares followed by bolls and leaves. Regarding mortality of different instars of S. litura, it was significantly more at higher nitrogen doses and it ranged from 83.04 to 96.27, 53.38 to 61.87 and 16.87 to 22.58% in case of S. litura one-day-old larvae, 3rd and 5th instar, respectively. While, non significant difference in mortalitywas observed during different sowing dates.