A practical handbook. This Health Cluster Guide (2nd edition, 2020) provides practical advice on how WHO, Health Cluster Coordinators and partners can work together during a humanitarian crisis to achieve the aims of reducing avoidable mortality, morbidity and disability, and restoring the delivery of and equitable access to preventive and curative health care. It highlights key principles of humanitarian health action and how coordination and joint efforts among health and other sector actors can increase the effectiveness and efficiency of health interventions and promote better health outcomes. It draws on Inter-Agency Standing Committee and other expert guidance and includes lessons from field experience in acute and protracted crises. The coordination principles and practice presented in Health Cluster Guide are equally valid for coordinators and members of health sector groups that seek to achieve effective health action in countries where the cluster approach has not been formally adopted.