Resumen 

We assess the long run effects of The Health Insurance for the Twenty First Century (SMSXXI) Program, part of Mexico’s Seguro Popular, that provides public health insurance for uninsured children under 5  years old. We show that the program led to reductions in out of pocket health expenditures by 13%,  primarily from expenses incurred on hospitalizations. Infant mortality by causes covered by the program were reduced by 5.3% and effects were largest in high baseline mortality areas. Long run health effects, approximately 8 years after the start of the program are reflected in a 0.44 cm average increase in height for birth cohorts exposed to the program, and anthropometric effects are almost 1cm on average for low-income populations. While no effects were detected on health service utilization, results suggest improvements in the quality of health care and specialized personnel are likely channels to explain final outcomes.