Kidney disease is a worldwide public health problem, affecting more than 850,000,000 persons, encompassing both chronic kidney disease (CKD) and acute kidney injury (AKI). Approximately 80% of people with CKD live in low-income (LIC) and lower-middle-income countries, within tropical regions. The nomenclature CKD of unknown origin (CKDu) or CKD of nontraditional causes (CKDnt) have been proposed for those who have no apparent etiology for kidney dysfunction, and usually are young males working in conditions that represents some risk for kidney injury, like heat stress, toxins, and environmental exposures. There is scant epidemiological data on CKD in most low-income countries due to few community-based studies, inconsistent assessments of kidney function, and a lack of mandatory registries. This chapter investigates CKDu and its interactions with tropical diseases.