The preference for sons has deep social, economic, and cultural roots in many East and South Asian societies. Historically, son preference has resulted in unusually high death rates for female infants and girls. Over the past 30 years, the introduction of prenatal screening technologies combined with widespread access to abortion has made possible the selective abortion of female fetuses. Resulting gender imbalances have led to concerns that a shortage of women will make it difficult for men to find wives. The Chinese, Indian, and South Korean governments have responded by making prenatal screening for sex identification illegal. China and India have also launched campaigns to improve attitudes toward girl children, and both countries offer small allowances to some parents of girls. Experience in South Korea indicates that sex-selective abortion peaks and then declines with social and economic modernization. Population projections and survey data suggest that falling fertility and women's reluctance to marry have a much larger effect than sex-selective abortion on the availability of women in the marriage market.