During the past 6 years, Mexico has undergone a large-scale transformation of its health system. This paper provides an overview of the main features of the Mexican reform experience. Because of its high degree of social inequality, Mexico is a microcosm of the range of problems that affect countries at all levels of development. Its health system had not kept up with the pressures of the double burden of disease, whereby malnutrition, common infections, and reproductive health problems coexist with non-communicable disease and injury. With half of its population uninsured, Mexico was facing an unacceptable paradox: whereas health is a key factor in the fight against poverty, a large number of families became impoverished by expenditures in health care and drugs. The reform was designed to correct this paradox by introducing a new scheme called Popular Health Insurance (Seguro Popular). This innovative initiative is gradually protecting the 50 million Mexicans, most of them poor, who had until now been excluded from formal social insurance. This paper reports encouraging results in the achievement of the ultimate objective of the reform: universal access to high-quality services with social protection for all.