Global studies of childhood cancer provide clues to cancer etiology, facilitate prevention and early diagnosis, identify biologic differences, improve survival rates in low-income countries (LIC) by facilitating quality improvement initiatives, and improve outcomes in high-income countries (HIC) through studies of tumor biology and collaborative clinical trials. Incidence rates of cancer differ between various ethnic groups within a single country and between various countries with similar ethnic compositions. Such differences may be the result of genetic predisposition, early or delayed exposure to infectious diseases, and other environmental factors. The reported incidence of childhood leukemia is lower in LIC than in more prosperous countries. Registration of childhood leukemia requires recognition of symptoms, rapid access to primary and tertiary medical care (a pediatric cancer unit), a correct diagnosis, and a data management infrastructure. In LIC, where these services are lacking, some children with leukemia may die before diagnosis and registration. In this environment, epidemiologic studies would seem to be an unaffordable luxury, but in reality represent a key element for progress. Hospital-based registries are both feasible and essential in LIC, and can be developed using available training programs for data managers and the free online Pediatric Oncology Networked Data Base (www.POND4kids.org), which allows collection, analysis, and sharing of data.