In 2012, a Guaranteed Health Plan for the private health system was submitted to the Chilean National Congress, with the aim of offering a standardized flat-rate health-care plan. This paper evaluates the impact that the introduction of this plan would have on the demand for health insurance. The results suggest that the private insurance portfolio would shrink by 12.39%, which means that around 400,000 people would switch to the public system, thereby exacerbating the adverse-selection problem faced by the system and imposing an additional fiscal burden of US$ 200 million per year.