We present results from a prospective 1-year random sample investigation of visitors to psychiatric emergency services covering the city of Copenhagen as a whole. The services are free of charge, are open 24 h a day, and offer psychiatric evaluation, acute treatment, and overnight stay for the population in each of the four catchment areas in the city. Every 10th day throughout 1985 all visits were registered. The demographic characteristics of 1969 visits (covering 1595 persons) are as follows: 75% were 20-50 years old, 59% were males, 65% were unmarried/divorced, and 37% were receiving disability pension. The predominant diagnoses were alcohol dependence (31% and schizophrenia (20% Among the repeat visitors these diagnoses were even more frequent. The results demonstrate that emergency services are necessary to prevent admission to a psychiatric ward, both for chronic patients and non-psychiatric individuals who need immediate assistance because of crisis reactions. Coordination of the emergency units in the city and a flexible cooperation with the regional social welfare system are essential for early interventions and optimal treatment of mental illness.