As in European countries a century ago, diarrhea is a major cause of child mortality in poor countries today. In Stockholm at the turn of the 19th century, political commitment, infrastructural investments in water and sanitation, and enforcement of sanitary improvements by a strong implementing organization helped eliminate diarrhea as a principal cause of death among children. These interventions also had an equitable impact on social class differences in diarrhea mortality, but not on overall mortality; overall mortality declined, but class differences remained. General infrastructural improvement and health education coupled with targeted interventions to vulnerable children may be successful in improving child health and reducing social differentials in mortality. Specific health care interventions may need to be complemented by infrastructural investments to improve water and sanitation if diarrhea mortality is to be further reduced in poor countries today.