High ratios of males to females in China have historically concerned researchers (Sen 1990) and their recent increase has alarmed policymakers worldwide. In this paper, I present a model of fertility choice when parents have access to a sex selection technology and face a mandated fertility limit. By exploiting variation in nes levied in China for unsanctioned births, I estimate the relative price of a son and daughter for mothers observed in China's 2000 census. I found that a son is worth .56 years of income more than a daughter, and the premium is highest among less educated mothers and families engaged in agriculture. I conclude with a set of simulations to predict the effect of revisions to China's fertility regulations, such as allowing all couples a second child and initiatives to subsidize parents who have daughters.