The resistance to phoxim of 21 strains of cotton bollworm, Helicoverpa armigera (Hübner), collected from field crops in 17 geographical locations in China during 1994-1995 was tested. Results showed that resistance to phoxim was widespread in the Yellow River Valley cotton area, Changjiang River Valley cotton area, Liaohe River Valley cotton area and South China cotton area. In comparison with the susceptible strain, the resistance of the strains from the Yellow river Valley cotton area, Changjiang River Valley cotton area, Liaohe River Valley cotton area, and South China cotton area ranged from 8- to 91-fold. However, no obvious phoxim resistance was detected in the strains from the northwest inland cotton area. After rearing in the laboratory for 22 generations without phoxim treatment, the phoxim resistance of the Wuxue strain collected from the Changjiang River Valley cotton area decreased from 27- to 9-fold, suggesting that to restrict uses of phoxim and its cross resistance insecticides in resistance regions may be an effective method for phoxim resistance management in China.