Building on the foundation of the three previous editions of Disease Control Priorities (DCP), published from 1993 through 2019, this new fourth edition, DCP4, uses a country-specific approach based on collaboration to summarize, produce, and help translate economic evidence into better priority setting and capacity strengthening for universal health coverage, public health functions, pandemic preparedness and response, and intersectoral and international action for health. Volume 1-Country-Led Priority Setting for Health-presents the overall lessons learned in defining and implementing essential health service packages (EHSPs). The volume is divided into three parts that highlight successes and failures and the way forward. • Part 1 focuses on the experiences of selected countries in developing their EHSPs, including Afghanistan, Ethiopia, the Arab Republic of Iran, Malawi, Pakistan, Somalia, and Zanzibar; Nigeria's Lancet Commission; India's Ayushman Bharat Health System Reforms; the success and failures of Colombia's health benefit package; and the evolution of priority setting in Mexico. • Part 2 presents cross-cutting insights on the development and implementation of EHSPs based on the experiences of Afghanistan, Ethiopia, Pakistan, Somalia, Sudan, and Zanzibar. It includes key steps and parameters for successful development and implementation; lessons learned related to costing and financing; monitoring and evaluation; and the role of the private sector in the development and delivery of EHSPs. • Part 3 presents three case studies: cross-national experiences on child health and development during school age and adolescence (the next 7,000 days), as well as the implementation of both the DCP3 essential noncommunicable diseases and surgery packages.