Gender preference, particularly son preference, is believed to sustain high fertility in many Asian countries, but previous research shows unclear effects. The authors examine and compare gender-preference effects on fertility in two otherwise comparable populations in Bangladesh that differ markedly in their access to and use of contraception. The authors find, as expected, stronger effects of gender preference in the population that has more access to contraception and contraceptive use. Thus gender preference may emerge as a significant barrier to further national family planning efforts in Bangladesh. The authors find that if a woman has at least one daughter, the risk of subsequent birth is related negatively to the number of sons. Women with no daughters also experience a higher risk of having a subsequent birth; this finding suggests that there is also some preference for daughters. Son preference is strong in both the early and later stages of family formation, but women also want to have at least one daughter after having several sons.