Three hundred and thirteen consecutive admissions to a department of respiratory medicine were evaluated in a prospective high-intensity monitoring scheme concerning adverse drug reactions or dose-related therapeutic failures as the contributing or sole cause of hospital admission. Eleven patients [3.5%, 95% confidence interval (CI) 2.0-6.2] were admitted because of adverse drug reactions. Only 3 of these patients manifested respiratory symptoms, while the remainder had various intercurrent nonpulmonary problems and were well known in the outpatient clinic, e.g. asthma or cancer patients. It is concluded that adverse drug reactions requiring admission rarely present as respiratory symptoms. Fourteen patient (4.5%, CI 2.7-7.4) were admitted because of dose-related therapeutic failures in all cases, except 2 with respiratory symptoms. Half of these were due to noncompliance. Analysis of theophylline samples taken on admission from 46 patients showed 25 (54%) to have concentrations below the therapeutic range of 55-110 microM, but contributed little to the identification of noncompliant patients. Eighty-three percent of the drug events were found to have been unavoidable. Nine patients admitted with acute asthma did not receive corticosteroids prior to admission (2.9%), all of which had therapy prescribed in general practice. The present study showed a comparatively low and hardly affectable prevalence of admissions caused by adverse drug reactions and dose-related therapeutic failure. However, therapeutic failure due to inappropriate choice of asthma medication, which was not included in this estimate, may be an important avoidable cause of admissions.