The earthquakes that hit Mexico City in September 1985 caused considerable damage both to the population and to important medical facilities. The disaster took place while the country was undertaking a profound reform of its health care system. This reform had introduced a new principle for allocating and distributing the benefits of health care, namely, the principle of citizenship. Operationally, the reform includes an effort to decentralize the decision-making authority, to modernize the administration, to achieve greater coordination within the health sector and among sectors, and to extend coverage to the entire population through an ambitious primary care program. This paper examines the health context in which the reform was taking place when the September earthquakes hit. After presenting the damages caused by the quakes, the paper analyzes the characteristics of the immediate response by the health system. Since many facilities within the system were severely damaged, a series of options for reconstruction are posited. The main lesson to be learned from the Mexican case is that cuts in health care programs are not the inevitable response to economic or natural crises. On the contrary, it is precisely when the majority of the population is undergoing difficulties that a universal and equitable health system becomes most necessary.