The effects of establishing an ease of access 'walk-in' service on General Practitioner referrals to the ambulatory services of a catchment area psychiatric service are outlined. The characteristics of the patients referred are described. GPs made immediate and sustained use of the walk-in service and its creation expanded use of the ambulatory services by an overall 50%. Individual GPs were found to use the ambulatory services disproportionately and to discriminate between their use of the walk-in service and the coexisting traditionally run outpatient clinic. The walk-in service also allowed patients to refer themselves; a policy which did not result in a flood of inappropriate referrals but enabled patients, already familiar with the service, to re-establish contact in times of distress. The findings are discussed in terms of the current growth of Community Mental Health Centres in the United Kingdom and their implications for GP/Psychiatric Service liaison.