Current understanding of the causes of under-5 childhood deaths in low- and middle-income countries relies heavily on country-level vital registration data and verbal autopsies. Reliable data on specific causes of deaths are crucial to target interventions more effectively and achieve rapid reductions in under-5 mortality. The Child Health and Mortality Prevention Surveillance (CHAMPS) network aims to systematically describe causes of child death and stillbirth in low- and middle-income countries using minimally invasive tissue sampling. The articles in this supplement introduce the set of foundational epidemiologic, demographic surveillance, social behavioral science, and laboratory methods. Undergirding the CHAMPS surveillance system designed to determine causes of child mortality.