Stable integration and spatio -temporal expression of two insecticidal genes (Cry1Ac and Cry2A) in transgenic cotton was studied. Firstly, integration of both genes was confirmed in these advance lines by different molecular analysis. The quantitative levels of both Cry1Ac and Cry2A genes were found variable among these cotton lines and also varied between different plant parts.  These lines showed a stable integration of insecticidal genes in T5 and T6 Progeny. The expression of both genes declined gradually with the age of plant as well as in different plant parts throughout the season. The leaves of Bt Cotton were found to have maximum expression of Cry1Ac and Cry2A genes followed by squares, bolls, anthers and petals. Toxin level in fruiting part was less as compared to other parts showing the in consistency in toxin level inspite of using 35S CaMV promoter which is constitutively expressing promoter. The study conducted suggested that CaMV 35S promoter is a developmental promoter and also it triggered research to find out new possible promoters to make expression of insecticidal genes consistent throughout life of cotton plant.