This retrospective study identified the clinical and epidemiological characteristics of patients coming to the emergency room of our hospital with exacerbated asthma or chronic obstructive pulmonary disease (COPD) in 1993 and 1994. We followed a previously established protocol to review the case histories of patients from both years. The 1,592 exacerbations we identified in 1,209 asthmatics accounted for 0.9% of all emergency visits, with a mean of 2.2 1.6 (0-9) visits daily. The 2,106 exacerbations of COPD in 1,208 patients accounted for 1.2% of all emergencies, with a mean 2.9 (1-12) visits per day. The mean age was 51.2 (14-93) years for asthmatics and 70.3 (29-96) years for COPD patients. Of asthmatics, 69.8% were women and 30.1% were men, whereas 91.4% of COPD patients were men. The readmission rate was 3.4% for asthmatics and 4.8% for COPD patients. The hospitalization rate was 26.7% for asthmatics and 49.4% for COPD exacerbation patients. The hospital saw 22.6% of asthma exacerbations between midnight and 8 a.m. and 41.6% of COPD exacerbations during the same time frame. For both diseases, more emergencies occurred in winter. Correlation between asthma and COPD and declared influenza cases in the community were r = 0.63 (p < 0.001) for asthma and r = 0.83 (p < 0.0001) for COPD. Our findings underline the considerable emergency care burden generated by exacerbations of obstructive airway diseases and suggest that community acquired respiratory infections are usually the underlying cause.