The World Health Organization (WHO) International Scheme to Evaluate Household Water Treatment Technologies (the Scheme) was established to independently and consistently evaluate the performance of household water treatment (HWT) technologies in removing microbial contaminants from drinking water. The scheme is part of the WHO normative programme of work on drinking-water safety. Results from the Scheme inform the selection by Member States and United Nations (UN) procuring agencies of effective HWT technologies to reduce the risk of diarrhoeal disease from unsafe drinking water. In particular, the Scheme helps to ensure products that provide limited or no pathogen removal are kept off the market.