Two thousand three hundred and ninety consecutive visits to a walk-in psychiatric emergency service were studied to examine issues relevant to service provision. Only a third of patients were from the catchment area. Psychotic patients and those admitted or kept overnight (guests) were more frequent after hours and among non-medical referrals, especially family and police referrals; but suicidal patients often came from other hospitals. At index visit a third of patients were offered follow-up, but attendance was poor. Factors influencing attendance were examined. Keeping overnight avoided unnecessary admissions. There was little evidence that patients abused the service. The findings suggest that a psychiatric emergency service should be available to all referrals 24 hours a day.