The Chinese government has just announced that China’s one-child policy has been lifted, to be replaced by a universal two-child policy. The implications of the one-child policy for modern China cannot be overstated. This policy has profoundly affected the lives of one-fifth of the world’s population for 35 years, at the most personal level of reproductive choice. In this Viewpoint, we describe why the policy was introduced (and why it may not even have been necessary); summarize the demographic, health, and social ramifications of the policy, both positive and negative; and consider whether this change is too late to address the demographic and social imbalances attributed to the policy.