Background: The aim was to examine mortality in psychiatric patients in Western Australia (WA), over a time period of considerable change in the delivery of mental health services. Methods: A population-based record linkage analysis was undertaken to quantify mortality among people with mental illness in WA. Mortality rates were calculated in users of mental health services and compared with rates in the whole population of WA. Trends in mortality were also examined using relative survival analysis, and proportional hazards regression. Results: The overall mortality rate ratio was 2.57 in males (95% CI: 2.51-2.64), and 2.18 in females (2.12-2.24). The highest cause-specific mortality rate ratio was for deaths due to suicide [RR: 7.37 in males (95% CI: 6.74-8.05) and 8.38 in females (959/0 CI: 7.11-9.89)], with mortality rate ratios being significantly greater than 1 for all other major causes of death. A relative survival analysis found that the excess mortality risk was concentrated in the first few years after first contact with mental health services. Proportional hazards regression analysis found a slight elevation of mortality rates over time. Conclusions: Mortality among psychiatric patients remains high and appears to be increasing. Highest excess mortality rate is associated with suicide, but mortality rates are significantly elevated for all major causes of death.