1) To know the impact of chronic obstructive pulmonary disease (COPD) on hospital care (visits to the emergency room and admission); and 2) to identify and describe COPD patients whose use of health care is high (COPD-HC), also assessing the costs generated by such patients. We reviewed the files of all patients with COPD receiving care at our hospital in 1998, looking at age, sex, smoking, simple spirometry, arterial gases at rest, number of admissions, duration of hospital stay, and number of visits to the emergency room. After describing the sample, patients were stratified in three groups by use of hospital care: group A, patients not requiring hospital care; group B, patients requiring less care than the COPD-HC group; and group C, COPD-HC. The criteria used to define the COPD-HC group were 1) >= 2 admissions in one year, 2) >= 3 visits to the emergency room, without admission in one year, or 3) 1 admission and 2 visits to the emergency room for COPD exacerbation in one year. Three hundred twenty cases were studied, 3 women (0.9%) and 317 men (99.1%), mean age 71 9 years. One hundred twenty-six patients (39.4%) made 263 visits in 1998, accounting for 1.1% of all emergencies (n = 23,750) and 4.05% of all medical emergencies (n = 6,489). Ninety-two patients (28.7%) were admitted for exacerbation of COPD. One hundred twenty-six admissions were made over the course of the year, accounting for 9.6% of all admissions to the internal medicine wards (n = 1,309). The 39 patients (12.2%) who were classified COPD-HC generated 160 emergency visits (60.8%) and 72 admissions due to COPD (57.1%). The analysis of variation revealed statistically significant differences among the 3 groups for age, FEV1, FVC and PaO2, but not for PaCO2. COPD-HC patients had the lowest values for FEV1, FVC and PaO2 and were older. COPD generates high demand for hospital care. A small group of COPD patients (12.2%) accounts for nearly 60% of hospital visits for this disease. The group requiring greater care generally has more severe disease (older, more severe bronchial obstruction and hypoxemia).