Objective: To compare rates of visits to a general practitioner between users and non-users of mental health services (MHS). Design, participants and setting: Population-based retrospective cohort study of 204 727 users and 294 076 matched non-users of MHS in Western Australia from 1 January 1990 to 30 June 2006, based on linked records of the use of MHS, hospital admissions, Medicare claims for GP and specialist services, electoral roll registration and deaths. Main outcome measures: Adjusted rate ratios (ARRs) for the number of visits to GPs by users of MHS relative to non-users, and for different categories of mental disorders. Results: Relative to non-users of MHS, the ARR of visits to GPs by users of MHS was 1.622(95% CI, 1.613-1.631) overall, and was elevated in each separate category of mental illness. ARRs were highest for alcohol/drug disorders, schizophrenia and affective psychoses (2.404, 1.834 and 1.798, respectively). The results were not changed by location (metropolitan, rural or remote addresses). However, the 4% of MHS users with no fixed address had a very low ARR of visits to GPs (0.058; 95% CI, 0.057-0.060). Conclusions: Users of MHS visit GPs substantially more often than non-users, with the exception of those with no fixed address who seldom see a GP at all. MJA 2010; 192: 501-506