For the most vulnerable, even small negative shocks can have significant short- and long-term impacts. Few interventions that improve shock-coping are widely available in sub-Saharan Africa. Researchers test whether individual pre- cautionary savings can mitigate a shock-coping behavior with potentially neg- ative spillovers: transactional sex. Sex for money is a common shock-coping behavior in sub-Saharan Africa and is believed to be a leading driver of the HIV/AIDS epidemic. In a field experiment in Kenya, researchers randomly assigned half of 600+ participating, vulnerable women to a savings intervention that consists of opening a mobile banking savings account labeled for emergency expenses and individual goals. The intervention led to an increase in total mobile savings, reductions in transactional sex as a risk-coping response to shocks, and a decrease in symptoms of sexually transmitted infections.