Homelessness has serious implications for the health of individuals and populations. Primary health-care programmes specifically tailored to homeless individuals might be more effective than standard primary health care. Standard case management, assertive community treatment, and critical time intervention are effective models of mental health-care delivery. Housing First, with immediate provision of housing in independent units with support, improves outcomes for individuals with serious mental illnesses. Many different types of interventions, including case management, are effective in the reduction of substance misuse. Interventions that provide case management and supportive housing have the greatest effect when they target individuals who are the most intensive users of services. Medical respite programmes are an effective intervention for homeless patients leaving the hospital. Although the scientific literature provides guidance on interventions to improve the health of homeless individuals, health-care providers should also seek to address social policies and structural factors that result in homelessness.