Since the introduction of the one-child policy in China in 1979, many more boys than girls have been born, foreshadowing a sizable bride shortage. What do young men unable to find wives do? This paper focuses on criminality, an asocial activity that has seen a marked rise since the mid-1990s. Exploiting province-year level variation, we find an elasticity of crime with respect to the sex ratio of 16- to 25-year-olds of 3.4, suggesting that male sex ratios can account for one-seventh of the rise in crime. We hypothesize that adverse marriage market conditions drive this association.