PURPOSE--Characterization of the population using the emergency unit of the Instituto do Coração--HCFMUSP. METHODS--The investigation was carried out in a randomly selected population of 225 people between January and April/93. To determine demographic profile, involvement of the accompanying people with the patient, the nosologic profile and patient's level of knowledge about the Social Health Security (SHS), a questionnaire was applied to the accompanying people. RESULTS--Of the 225 patients, 52.4 were males; age ranged from 1 day to 93 years (45.5 over 60 years old); 61 were living in the state of São Paulo; 17 were professionally active; 52 were beneficiaries of Social Security; 92.4 were users of SHS; 47.3 were illiterate; 67 presented with acute cardiovascular diseases and 33 with a noncardiologic diagnosis. CONCLUSION--This is an old population with a low level of instruction, coming from all regions of the country. Because SHS medical services and hospitals does not work well, including cardiology services, this population asked for care in our emergency unit.