The authors study two interventions in Beijing, China, that provide patients with information on antibiotic resistance via text message to discourage the overuse of antibiotics. The messages were sent once a month for five months. One intervention emphasizes the threat to the recipient's own health and is found to have negligible effects. The other intervention, which highlights the overall threat to society, reduces antibiotics purchases by 17% in dosage without discouraging healthcare visits and other medicine purchases. The results demonstrate that prosocial messaging can have the potential to address public health issues that require collective action.