The toxicity of Indian transgenic Bt cotton cultivars viz., RCH 2, RCH 20, RCH 134, RCH 138, RCH 144, MECH 12, MECH 162 and MECH 184 to the cotton bollworm, Helicoverpa armigera were studied under laboratory condition. Result of the study reports that, among the Bt cotton cultivars, the toxicity and larval growth inhibition for first instar, second instar and third instar was higher, when larvae fed on leaves, squares and bolls of RCH 144. The effects of different Bt cotton cultivars on growth, consumption, digestion and utilization of the cotton bollworm, Helicoverpa armigera was also studied under laboratory condition. A time series comparison of feeding by second and third instar larvae of H. armigera indicates that leaf area damage was significantly highest in non transgenic Bt cotton (MECH 162 and RCH 2) compared to non transgenic Bt cotton. Among the Bt cotton, leaf area damage was lowest in RCH 144 and third instar larvae fed more area than second instar larvae. In general, the food intake, faecal matter voided and weight gained by the larvae were lower in transgenic Bt cotton cultivars compared to in non transgenic Bt cotton. The present study report the larvae subjected to RCH 144 Bt cotton cultivar have lower food consumption, consumption index, growth rate, efficiency of conversion of ingested food, efficiency of conversion of digested food and highest approximate digestibility than RCH 2, RCH 20, RCH 134, RCH 138, MECH 12, MECH 162, MECH 184, non Bt RCH 2 and MECH 184 in leaves, squares and bolls, respectively. Finally, the applicability of these studies in corresponding to the management of H. armigera in sustainable cotton production system is discussed.