Emergency water treatment approaches relying on coagulation vary from centralised modular and portable "kits" to "point-of-use" or "household" interventions. Typical coagulation practice in emergencies is reviewed in view of field constraints (e.g. equipment and resources) and contrasted with underlying theory and conventional water treatment procedures. Examples of coagulation in emergencies are also presented based on documented field experiences alongside the discussion of other relevant issues such as process control, sludge production and management, case of use, and aluminium coagulant residuals in finished waters.