The purpose of this article is to explore the connection between household composition and infant mortality in the first half of the twentieth century in Taiwan. The research results claim that illegitimate infants have higher death risk than legitimate infants; that contrary to expectation female infants have mortality rates as high as boys; and that same sex sibling order effects are approximately same among boys and girls. The significance for infant mortality of the sex of household head is the other major finding of this article: female-headed families have higher rates of infant mortality.