The association between schizophrenia and diabetes has been recognized for well over a century, but the underlying reasons for this association are unclear. In October 2003, an international group of diabetologists and psychiatrists met to review the literature relating to the association, and to create pragmatic guidelines for the management of diabetic risk in patients with severe mental illness. Since that meeting, over 100 additional papers have been published on the association between glucose abnormalities and schizophrenia, and this is a clear reflection of the level of interest in this clinically important area. Diabetes is highly prevalent among the schizophrenia population, but most sufferers remain undiagnosed in the community. The reasons why individuals with schizophrenia are more prone to developing diabetes than the general population are poorly defined, but likely to be multifactorial. The role of antipsychotic medications in the development of diabetes and other pre-diabetic states remains controversial, but it appears that the attributable risk is low. Traditional risk factors most probably account for much of the diabetes seen in schizophrenia populations, suggesting that routine screening and aggressive risk factor management are especially important in this patient group.