This paper discusses contraceptive use and discontinuation among women in north Vietnam, in the context of a strong cultural preference for sons and astringent two-child population policy. Among a random sample of 1432 married women aged 15–49 in a rur al province in north Vietnam in 1994, nearly 60 percent used the intrauterine device (IUD) for contraception; other modern methods were hardly used at all. Overall discontinuation rates were high -nearly 45 per cent after three years; the most common reason was expulsion. Women without sons reported significantly higher rates of IUD discontinuation due to expulsion and contraceptive failure than women who had a son. We interpreted this as an indication that women without sons had deliberately removed the IUD and reported this as an expulsion or contraceptive failure, in hopes of satisfying their families' wish for a son, while avoiding the criticism of deliberately exceeding the two-child limit. Assessments ofmedical technology usually consider only clinical and service aspects. A gender analysis of contraceptive effectiveness data that also takes into account the social, cultural and political context can offer insights into the complexities of women's reproductive lives and the contradictory demands on their fertility.