This handbook focuses on the requirements of the implementer. Its aim is to provide a concise resource for approaching and handling geogenic contamination (primarily arsenic and fluoride) in groundwater used for drinking and cooking purposes. It provides information on water quality testing, different treatment options and practical guidelines, including draft questionnaires, on the integration of technical, institutional and sociological aspects of the problem. Its aim is to promote the sustainable mitigation of health issues related to drinking water contaminated with arsenic or fluoride.