This Health cluster guide highlights key principles of humanitarian health action and how coordination and joint efforts among health and other sector actors working in partnership can increase the effectiveness and efficiency of health interventions and promote better health outcomes. It draws on Inter-Agency Standing Committee and other documents but also includes lessons from field experience. Although addressed to health cluster lead agencies, coordinators and partners, the guidance is 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. The guide should be useful in different humanitarian crisis contexts, including sudden onset and slow onset crises and protracted emergencies. It does not address all the specificities of the different contexts.