Using data from two surveys in three counties among which the prevalence of uxorilocal marriage varies greatly, this paper analyzes effects of marriage form, as well as individual, family, and social factors on son preference in the context of strict birth control in rural China. It is shown that, under the Chinese patrilineal joint family system, son preference can be inferred from the reproductive behavior of couples in virilocal marriage but not from that of couples in uxorilocal marriage. However, the negative effect of uxorilocal marriage on son preference is likely to depend on other factors. For all three counties, women married after the 1990s are less likely to have preference for sons; in regions with low prevalence of uxorilocal marriages, son preference is stronger for virilocally married couples with more sisters or having first birth at older age, and for couples whose marriages were arranged by others; in regions with high prevalence of uxorilocal marriages but under-developed economies, higher educated women in uxorilocal marriages have stronger son preference. Son preference differs greatly among the three counties and increased prevalence of uxorilocal marriage may significantly weaken son preference. These findings relate to changes in rural family and marriage customs during the current demographic and social transition, and suggest new approaches to weakening son preference while maintaining low fertility in rural China. (Contains 3 figures and 2 tables.)