The field experiment was conducted during kharif  2008 and 2009 at Punjab Agricultural University, Ludhiana to study the effect of various plant populations and fertilizer levels on Bt toxin content in Bt cotton. The results showed that Bt toxins levels were not significantly affected by plant population at all  stages of crop growth. However, Bt toxin level increased with increased fertilizer doses at all stages of the crop growth. Significantly higher Bt toxins were recorded in 150 per cent RDF as compared to RDF at 60 and 90 DAS during 2009 and 90 DAS during 2008.                                                                                                                    