China has the most severe shortage of girls compared to boys of any country in the world today, as documented by China's surveys and censuses up to 2000. This article evaluates data on sex ratios in China since before the founding of the People's Republic, and shows that the relative dearth of girls has become more extreme during the last two decades, and that the problem is real and not merely due to undercounting of girls. Daughters are lost primarily through sex-selective abortion, secondly through excess female infant mortality, and thirdly through neglect or mistreatment of girls up to age three, in cities as well as rural areas. Until recently, the dearth of girls was confined to second or higher-order births, but now couples in some provinces are using sex-selective abortions for first births. Maps show the geographical concentration of life-threatening discrimination against girls and its spread over time. Son preference, low fertility and technology combine to cause the loss of daughters in China today and compulsory family planning and the one-child policy exacerbate the problem. The discussion includes what the People's Republic of China has done to ameliorate life-threatening discrimination against girls and what further steps might be taken to improve the situation.