Recent mental health care policy has addressed the need for health care professionals to consider the physical health of consumers. Mental health nurses are particularly well-placed for this role. To provide mental health nurses with practical information, this narrative review summarises evidence from recent research on the physical health of individuals with Serious Mental Illness (SMI). In those with SMI, the international prevalence of obesity, the metabolic syndrome, diabetes mellitus, symptoms of cardiovascular disease, and respiratory disease all exceed that of the general population by at least two times, and HIV prevalence may be increased by as much as eight times. This increased prevalence of chronic disease may be largely responsible for an increased risk of death of up to five times, resulting in as much as 30 years of potential life lost. Of particular concern, the recent evidence suggests that for physical health and increased mortality, the gap between individuals with SMI and the general population is worsening. Unhealthy lifestyle behaviours undoubtedly play a role in the development of poor physical health and chronic disease, and the present review indicates that low physical activity, poor diet, smoking, alcohol and substance abuse, and risky sexual behaviour are common in individuals with SMI. This narrative review demonstrates that the prevalence of poor physical health and health behaviours in people with SMI far exceed that observed in the general population, and reinforces the urgent need for mental health nurses to address physical health concerns in patients.