Psychotic illness and its treatment are associated with an increased rate of diabetes and worsening blood sugar control, Australia. The newer, second-generation antipsychotic agents are more likely to produce this effect than the first-generation agents, but both contribute to the problem. The effect is usually related to insulin resistance through weight gain, but other mechanisms may exist. Diabetic ketoacidosis is rare. Management of psychosis takes priority over concerns about the potential metabolic sequelae of treatment, but the prevalence of the latter requires that all patients taking antipsychotic agents be actively screened and treated. Patients treated with antipsychotic agents need baseline and regular checks, including weight, blood glucose and lipid levels and blood pressure. Management of psychosis with its attendant medical problems requires a multidisciplinary approach, with primary health practitioners playing a central role. Mortality and medical morbidity is higher in those with psychosis than expected; preventive measures, combined with early detection and treatment of hyperglycaemia and other metabolic problems, is a key public health issue.