This fourth revision of the manual reflects recent clinical experience and research findings in diarrhoea case management. Compared to earlier versions, it includes revised guidelines on the management of children with acute diarrhoea using the new reduced (low) osmolarity ORS formulation and using zinc supplements, which have been shown to reduce duration and severity of diarrhoeal episodes, and revised guidelines for the management of bloody diarrhoea. Guidelines in the manual are based on the revised WHO chart that are included at the end of this document.