In this Review, we look at the relation between bereavement and physical and mental health. Although grief is not a disease and most people adjust without professional psychological intervention, bereavement is associated with excess risk of mortality, particularly in the early weeks and months after loss. It is related to decrements in physical health, indicated by presence of symptoms and illnesses, and use of medical services. Furthermore, bereaved individuals report diverse psychological reactions. For a few people, mental disorders or complications in the grieving process ensue. We summarise research on risk factors that increase vulnerability of some bereaved individuals. Diverse factors (circumstances of death, intrapersonal and interpersonal variables, ways of coping) are likely to co-determine excesses in ill-health. We also assess the effectiveness of psychological intervention programmes. Intervention should be targeted at high-risk people and those with complicated grief or bereavement-related depression and stress disorders.