Field populations of Helicoverpa assulta (Guenee) (Lepidoptera: Noctuidae) from the main tobacco-growing regions of China were investigated for their resistance to the conventional insecticidal chemicals fenvalerate (pyrethroid), phoxim (organophosphate), and methomyl (carbamate) during 2004-2005 using a micro-topical method under laboratory conditions. The studied strains exhibited an increased resistance to fenvalerate by 5.83-17,622-fold compared to the control strain. The highest levels of resistance to fenvalerate were 1042-17,622-fold and observed for 12 out of the 25 studied strains. Four strains showed a resistance level increased by 189-823-fold and 5 strains showed very low resistance to fenvalerate (<10). Substantial resistance to phoxim was observed only in one strain (50.8-fold), which was collected from Anhui in East China (AH1). Significant resistance to methomyl was detected in two strains with increases of 37.1- and 31.6-fold, respectively. These were collected from Anhui (AH1) and Yunnan (YN1) in East China and Southwest China. The impacts of H. assulta resistance to these insecticides on its management in China are discussed.