Background Most studies of mortality in psychiatric patients have investigated in-patients rather than those attending out-patient clinics or primary care, where most receive treatment. Aims To evaluate the mortality risk in mental illness for patients in contact with psychiatric services or primary care (n=221 048) across Nova Scotia (population 936 025). Method A population-based record-linkage analysis was made of the period 1995-2000, using an inception cohortto calculate mortality rate ratios. Results The mortality rate was 1.74, with increased ratios for all major causes of death. Male mortality was almost double that of females after controlling for demographic factors, treatment setting and place of residence. Patients of lower income, in specialist psychiatric settings, and with dementia or psychoses were also at greater risk. However, in absolute numbers, 72% of deaths occurred in patients who had only seen their general practitioner. Conclusions Mortality risk is increased in all psychiatric patients, not just those who have received in-patient treatment.