Oobjectives: To evaluate the effectiveness of a program aiming to decrease the sex ratio at birth in 3 districts of Sac Giang province. Subjects and methods: Group-based intervention with pre- and postcomparison on 400 couples who gave birth from May to the end of August 2013, in 3 districts Luc Nam, Lang Giang, and Viet Yen districts of Sac Giang province. Results: The knowledge about the consequence of having more boys than girls (making men difficult to find their partners) increased by 8.1 percent; the prevalence of subjects thinking that sex-ratio imbalance did not influence the society reduced by 8.3 percent. Attitude: Prevalence of respondents who wanted to have a son decreased by 14.6 percent and that of those who had no concerns about gender of the baby increased by 5.8 percent. Practice: the prevalence of respondents utilizing the fetal sex selections in the nearest birth decreased by 9.2 percent. Sex ratio at birth in Sac Giang province decreased 2.3 percentage points; Sex ratio at birth in all three districts decreased in all birth-orders.