Nitrate content of groundwater was surveyed from 1999 to 2000 in the rural plain areas of Beijing.The mean value of NO₃^--N content of groundwater sampled from 481 wells was 5.74 mg L^-1, NO₃^--N content in 48 1 4% of the wells was above 2 mg L^-1, implying that the quality of groundwater was affected by human activities, 21.0% above 10 mg L^-1, which is the maximum permissible limit for drinking water, and 8.1 percent above 20 mg L^-1.The surveyed wells were grouped into two types based on depth and utilizat ion, that is, drinking wells(DW), about 120 to 200 meters in depth, and irrigation wells(IW), about 70 to 100 meters in depth.NO₃^--N contents of groundwater from 145 DWs and 336 IWs averaged 5.16 mg L^-1 and 5.98 mg L^-1 respectively, and 13.8% of DW and 24.1% of IW exceeded 10 mg L^-1.Nitrate contamination of groundwater in the suburbs of Beijing, such as Haidian, Fengtai and Chaoyang Districts, is much worse than that in the exurbs of Beijing, such as Shunyi, Tongzhou, Changpin, and Daxing Districts.For suburban areas, NO₃^--N content in 38.7% of DW and 52.6% of IW were above 10 mg L^-1, but for exurban areas, only 3.0% of DWs and 15.3% of IWs above 10 mg L^-1.It is confirmed that nitrate contaminated wells were mainly located in the long-term vegetable cultivation regions.In general, nitrate contamination of groundwater in Beijing is more serious than in developed countries, and hence it is necessary to take countermeasures to control nitrate pollution.